A Short Diatribe on Even Ends

Before diving in, I want to mention Ken Pomeroy's new curling website DoubleTakeout.com . Ken is an esteemed analyst of US college basketball and in recent years caught the curling bug. You can hear how he came to the sport in his interview on a recent episode of the Rocks Across the Pond podcast. Thank you to Ken for recharging my CurlWithMath batteries and despite podcasting and other projects on the go, I will be trying to post more here than I have in recent years, including an updated Win Probability chart and revisit to a classic article "Is Curling a Battle for the Hammer?". 

As I wrote in a past Curling News (also released on this blog) we need more collaboration in analytics to move the sport further ahead and I'm thrilled to see Ken bring his court-side math chops to the ice with painted rings. Now on with the article....

If you've watched curling on television in the last few years it's very likely you've heard a commentator mention the term "even ends".  Perhaps you wondered what it meant.  Or maybe you felt like an insider because you recognized the great decision a team made to carry over their hammer into an even end to improve their chance at victory.  If you are in the latter category, then I'd like you to consider that the team may in many cases be making an irrelevant choice which neither increases or decreases their chance at victory, or possibly a mistake.

I am not going to quarrel with blanking an end when you are tied or ahead with hammer at any point in the game. Generally, this either improves your position or has limited or no impact on the outcome. I won't discuss the irrelevance of blanking the first end to get the hammer in the second (an "even") end.  Choosing to blank the first end may or may not be a great decision, depending on many factors, such as opponent, ice conditions, style of play or the number of cocktails you had the night before. But please don't say you blanked the first end because "2" is an even number and you are expecting to trade hammers for the next 7 or 9 ends. 

I want to look specifically at a team one down with hammer, charting their strategic course when 4 ends remain in the contest.  Specifically, the 7th end of a 10 end game, or 5th end of an 8 end game. When behind by a single point in this situation, some teams are maneuvering the play to increase their chance for a blank, in order to enter the final three ends and get "two hammers to one".  It sounds exciting doesn't it?  A blank in this fateful end appears to mean you get twice as many hammers than your opponent.  What this concept misses, however, is you have hammer right now and many things can still happen to thwart your comeback. Steals happen. Three enders happen. And sometimes, no one scores and the hammer doesn't come back to you when you thought it would. You can also become predictable and if your opponent knows what you are planning to do, they may gain a strategic advantage.

I've written before on this topic and even submitted a paper to the MIT Sloan Sports Analytics Conference in 2014 that included some analysis.  Without re-hashing it, I'll summarize by saying it's simply not that substantial a difference. The study indicated a weaker team improves their chances by blanking against a stronger opponent, the stronger team is better to stay aggressive and if two teams are equal, it really doesn't matter. 

Team Mike McEwen made a decision in the Wild Card game ahead of the 2020 Brier that came straight out of the Even Ends playbook. Trailing Glenn Howard 3-2 with hammer in the late stage of the 7th end, Mike made no hesitation in peeling a corner guard with his first stone, rather than choosing to come around and attempt to score a deuce.

McEwen is Red

I can appreciate some aspects of the situation might be a concern. The guard is tight to the rings and is a Howard stone. If Mike makes a perfect come around, the greatest risk is Glenn playing a straight back raise and nutting it, forcing McEwen to either draw for one or attempt a difficult raise take-out in order to blank the end. My suspicion, however, is Mike may have chosen to peel the guard regardless of the colour or location of the stone. I recall a similar scenario later in this Brier where a team chose to peel their own guard in the 7th end (or, in a hazy state of quarantine I might have dreamed this since I cannot locate it on Curling Canada's YouTube channel). Let's consider Mike's options...

Peeling the guard will result in a blank nearly every time, so we'll assume 100%. WP = 42%. We'll also assume a draw attempt by McEwen will hit the paint somewhere.

If Mike is able to score two points, his WP increase to 63%. But failure to score two and being forced to a single will result in WP = 37%. Math would suggest it's preferable to score two right now and all the advantage sits with Mike. He has two rocks to Glenn's one and barring a horrible mistake, no fear of a steal. So what might happen if Mike chooses to draw instead?

If McEwen makes a perfect come-around, as stated earlier, Glenn is most likely to attempt a run-back. The only risk in this case would be a perfect nut-nut with Glenn raising his guard perfectly and sitting completely buried. If he's able to accomplish this, Mike would be faced with a draw for one or run-back for a blank, introducing more risk that he has right now. Any other instance in which Glenn makes the run-back (ie. most of the time) and is not buried, it's a blank end.

If Mike makes a poor shot and comes behind the tee line, Glenn may choose to draw down and freeze to the McEwen stone and again, Mike may be forced to a single. However, sometimes McEwen comes deep and Glenn makes a poor shot, leaving them a chance for two points.

What if Mike makes a perfect draw every time? Let's consider Glenn makes a the nut-nut run-back 10% and misses 20%. Mike increases his WP to 46%. In fact, if Mike NEVER get 2 points, and Glenn makes the nut-nut an astounding 20% of the time, his WP still only drops to 41%!

Now, let's estimate Mike comes deep on the draw 30% of the time and Glenn draws down on top and is able to force 90% of the time this happens. Adding to the scenario above, his WP = 47%. Note this is a very conservative approach as Mike should be considered comparable or even more accurate than Glenn at this stage of their careers and those estimated percentages are likely more in his favour.

Some readers might consider a third option for Team McEwen. Mike could draw mostly buried, leaving Glenn a small piece of granite. This increases the likely-hood Glenn will try to hit the stone and roll to the open, forcing a blank, introducing some risk of a missed shot and deuce for McEwen. Also makes the perfect runback much more difficult. Not certain the slim chance of Glenn wrecking on the guard is worth the attempt, but others may disagree.

Looking at these numbers, I can understand McEwen's rush to peel the guard as it eliminates any variability in a game that means everything (win you're in the Brier, lose you go home). It's fair to say the decision in a vacuum is not so clear and I would hope, if the guard was a Red instead of Yellow, Mike would not so quickly toss aside a possible skip's deuce, simply because it was the 7th end. One can only wonder what they would have done in the same situation one end later?

You can watch the situation unfold here... https://youtu.be/se8IveYx9UY?t=5727

Episode 68 - Lindsay Sparkes

Lindsay Sparkes was driven by a desire to improve rather than by competition. Leaving figure skating for curling she replaced judges with a scoreboard and by focusing on her own ability, eventually the winning took care of itself. Joined by childhood friends Dawn Knowles, Robin Klassen and Lorraine Bowles, Lindsay skipped her young team to the Provincial and Canadian Championship in 1976. They repeated in 1979, with the added pressure of representing Canada at the first ever Women's World Championship in Perth, Scotland. Lindsay shares stories from those early years and her later success, winning the Worlds and Olympics with Linda Moore, and why she stepped away from competition and became a national coach.

Check out the latest episode of Curling Legends Podcast

Episode 67 - Glen Jackson/Doug Wilson

Glen Jackson was young and brash but made a mature decision when it mattered. A coin flip to determine who would be third for Paul Gowsell on their high school rink went to Neil Houston and Glen chose to stay with the team. Joined by Kelly Stearne at lead, the long haired teenagers with their push brooms would go on to win Canadian and World Junior Championships while taking home cash from some of the greatest teams of the era. Glen shares his version of legendary Gowsell stories like the van, the Van Winkle, the dog and the pizza. Before talking to Glen (30:45), I speak with transplanted Canadian living in Scotland, Doug Wilson (4:02). Doug works through his personal psychoanalysis of curling strategy with other curling fans on his Facebook group Daily Curling Puzzle.

Check out the latest episode of Curling Legends Podcast

Episode 66 - Matt Hames/Warren Hansen

Matt Hames was a mad man. Once a copywriter, just like fictional TV character Don Draper, Matt gave up three martini lunches at Bay and Bloor for six packs and road trips to bonspiels in Thunder Bay and a chance to make the Olympics. After falling short to reach the 1997 Olympic Trials with John Base, Matt landed with Scott Patterson and kept pursuing curling for a time, but eventually life took him to Upstate New York. We discuss Matt's journey and also how we met; not on the ice in 1995 when I lived in Toronto, but on his Curling Zoom party, which has become a twice weekly event during the COVID-19 pandemic. Before talking to Matt (40:57), I catch-up with my guest from Episodes 7 and 8, Warren Hansen (14:55). We discuss his new podcast with Kevin Martin, Inside Curling (hosted by Jim Jerome), and delve into Canada's Curling Hall of Fame. We also discuss rule changes, such as freezing a centre guard to discourage the tick-shot. My article that examines this rule (mentioned in the show) can be found at http://curlwithmath.blogspot.com/2020/05/ruling-final-end.html

To find out how to join Matt's Zoom Curling Rewatch, go to https://www.facebook.com/curlinglegends

Check out the latest episode of Curling Legends Podcast

Ruling the Final End

There's been plenty of discussion recently on whether the WCF should shorten all events from 10 ends down to 8. But there is another consideration that's floating in the curling ether that could perhaps more dramatically alter the sport. This rule was used in the now defunct Elite 10 match play format for all ends and some people pondered its use in "regular" curling as a change for possibly all ends or maybe just the final end (or extra end). The Champions Cup adopted this version of the rule for last year and would have used it again this spring if not for the COVID-19 pandemic.

The rule allows for a lead rock placed on the centre line to not only be in the free guard zone, but to be considered frozen in place on that line and unable to be moved by the opponent until the 6th rock of the end. Rather than play a tick shot and move the centre guard away from play, a team tied with hammer would now be forced to another strategy, invariably putting more rocks in play during the end. The reason this rule is being discussed stems from the increasing proficiency with which teams can execute the tick shot. With continued improvement in skill the shot will become so routine a team without hammer will never be able to put pressure on the opposition and a tied game in the final end will become an anti-climactic victory for the team with hammer. The fear is dramatic final ends will increasingly become routine, too repetitive and lower competitive balance.

The reasons for tweaking curling rules over the past 25 plus years has been to balance a fair test of competition with an entertaining contest that keeps fans interested in the outcome. When ice conditions, push brooms and skill level surpassed the point at which traditional rules were entertaining, the sport had to shift to a new rule (Free Guard Zone) in order to keep its appeal and continue to grow globally. I sometimes ponder if ice conditions had not improved and mixing broom use was allowed during a game (as seen in the 1980s and early 90s) everyone might have held off on these new rules (though probably not) and the game could have remained entertaining to fans, if partly due to the odd fight between teams over an alleged 7-up dipped corn broom.

But here we are. Three rock (in Canada) went to 4 rock and now 5 rock and it appears we have a great game that is enjoyed by many and growing around the globe. So, the first question to be asked is why change?  Firstly, I don't want to disparage the consideration. It is good practice to continuously consider how change can improve a sport. The three-point line, changes to the hand-check rules in the NBA and various NFL rules starting from the mid-70s in order to increase passing, have changed these sports for the better and improved their entertainment value. Any debate on the dreaded neutral zone trap in the NHL has hopefully disappeared. Sometimes mistakes are made (see late 90s NBA shorter three-point line), but in general I applaud sports attempting to improve as its athletes, fans and conditions change. In the case for curling, the part of my brain that yells at kids to “get off my lawn” thinks the sport has experienced so much change in the last 30 years that we've become addicted to thinking it constantly needs altering for the sake of change rather than just enjoying it for what it is. If people spent more time on growing the sport by getting more people to "play it", rather than focus ad nauseum on changes to make to it, in their perspective, "better", the sport would be further ahead. Instead of arguing for further on ice changes, could we possibly improve the arena and live viewing experience and get more butts in seats?

Perhaps part of this behaviour is simply because curling has changed so much over the past few decades that we all feel a need to constantly tweak and alter its form out of habit. We live in a sports world where the audience doesn’t simply watch games but derive pleasure in becoming an agent, general manager or owner while tweeting from their couch. In a culture of daily fantasy sports, fans are programmed to analyze who should be traded and what contract a superstar should receive in order to meet complex salary cap rules, most of which they understand. Perhaps talk of rule changes can garner attention in a crowded sports and entertainment landscape, but part of me wants some of this debate on what's wrong with curling to take a backseat for a while.

I heard someone ran a bonspiel in Switzerland in which blanking meant losing hammer the following end. This is one of a few concepts thrown around over the years to reduce zeroes on the board and generate more scoring. This nonsense needs to stop. If you want to create a different version of the sport (a la Mixed Doubles), fine, but you cannot remove blank ends without fundamentally altering the standard format of the game. The very nature of a blank end is what provides a subtle but very significant strategic attribute to curling not seen in other sports. Curling has never been a game where scoring the most matters or provides the greatest entertainment. Curling is a game of point differential. Each contest is a drama that unfolds over several ends, with every story looking very different than the last. Sure, an end in which a team puts their first rock into the rings and both adversaries decide to hit through to a blank is not entertaining. But find me a game in the past decade where two teams have done this for 3 ends, much less 8 or 10. The blank ends I've witnessed in the free guard zone era involve intricate shot decisions and execution throughout, often including a double take-out, sometimes on the final shot. At each stage of these ends, a team needs to contemplate whether to focus on offense with aggressive shot selection in an attempt to score two or more (risking a force or steal) or shift to a defensive strategy despite their opponent trying to create the opposite result. I've seen top teams in a Grand Slam call a timeout and discuss whether to peel or add another guard, and then watch their opponent do the exact opposite of what they had expected on the very next shot. If a team cannot blank, all of this disappears and we are left with a modified scoring version of skins curling, except the team without hammer has no incentive to force a single point from their opponent. Now the team without hammer will play defensive and instead of zeroes on the board we'll see a row of ones. The score might be higher, but the entertainment value will not. The very nature of curling is a battle for the hammer and if that aspect disappears, the game is no longer the same. Luckily, as I understand, most involved in this Swiss bonspiel did not find the new rule to be of interest. The next time someone complains about too many zeroes on the score sheet, ask them if they watched the game. I'm certain there were rocks in play, great shots to admire and enough tension to keep them from changing channels.

Back to our original debate on outlawing the tick shot in the final end. Rather than remain a cranky old codger, I'll keep an open mind and examine the data. Looking at major league baseball results since 1957, the home team wins a tied game starting the 9th inning 52.07% of the time. In curling, a tie score in the final end is simply not close to a "tied" likely outcome. Curling is closer to a tied ballgame in the final inning when a team is behind by one point with the hammer. The general rule of thumb is the team ahead one point without hammer is 60% likely to win (58.7% for men and 57.1% for women over the last 4 seasons). This is actually very close to baseball odds for the home team to win with one out and no runners on base at the top of the 9th inning (57.9%).

Looking at the last 4 seasons of world ranking events, men’s teams win 75.2% of the time starting with hammer in the final frame of a tied game while women’s teams win 70.5% of their contests. At the higher levels (Grand Slam and Canada Cup data specifically, excluding Tier 2 and the 2019 Champions Cup), over that time frame the results are 84.4% and 73.2% respectively.

Back to our baseball analogy; if we begin the 9th inning with the visiting team ahead 1 run, odds for victory for the home team are only 15%. This appears worse than that of a team tied without hammer. No one is suggesting that the team that's one run down should be given a free runner on first base to start an inning, so why provide an advantage to the team that's behind at this point?  One argument is that a team which starts the game tied without hammer has not lost any position on the scoreboard but is now at a greater disadvantage. That is true, but as stated before, curling is a battle for hammer. This is specifically why teams now compete to determine hammer in the first end rather than have it decided by a coin flip.  However, major league baseball results are consistent from 1957 to 2018. You can choose any 5, 10 or 30 year stretch over that span and it's roughly within one percent. Curling teams keep getting better and the hammer advantage appears to be increasing in this tied-at-the-end situation, at least for the top teams in the world.

One further consideration that cannot be measured in math (yet), is the fan aesthetic. A baseball team starting the last inning one down can lose many ways. A runner could reach first and steal second, a bunt, maybe a double play, anything is possible.  Even striking out the side against the top of the batting order can be thrilling. In curling, the broadcaster may come back from a TV commercial, both tick shots have already been made, and any further dramatic tension has been taken from the contest, like the air from a balloon. A baseball team down a run in the 9^th inning may lose more often than the team starting the final end without hammer, but the potential for entertainment value is significantly higher.

Under the 5-rock free guard zone, when top teams have an option, some are now choosing to be 2 down with hammer in the final end rather than tied without. At first this appears to be an error as the odds to win have only improved slightly since the end of the 4-rock rule (about 11 to 13% for men and 14 to 16% for women). These results still appear to be worse than a 25% or 30% chance to win when tied. The real scrutiny comes for the very top teams. Looking at more recent data, in the toughest events, men’s teams have gone 73-7 (91.3%) since the start of the 2018-19 season when tied with hammer in final or extra end.  

Given recent results, it's no wonder Kevin Koe prefers to be 2 down with hammer rather than tied without at the end of a game. Grand Slam women teams in 2018-19 tied at the end with hammer reached a record of 46-5 (90.2%). However, this past season teams were 34-15 (69.4%) which is in line with the broader series of world ranking events and historical results. Always the danger of small sample sizes, we see women were 91.3% in the 2014-15 season, but this came in a mere 23 situations. Women’s teams should nearly always prefer to be tied without rather than down 2 with hammer in the final end, but for how much longer?

It's fair to say these recent numbers are a concern and something to keep a collective eye on. To be clear, I hate the idea of changing a basic rule at the end of a game. I'm at a loss finding a comparison from elsewhere in the sports world, other than perhaps regular season NHL overtime. Everyone has an opinion on the various changes this century (shoot-out, 3-on-3, 4-on-4) but most would concur that when the play-offs arrive, when it really matters, these tweaks are thrown aside, and the game is played on. Though recent results could be an indicator of an undesirable future, concerns appear to be only with the very top men’s teams over a short period. I'd not suggest we change a rule for all because of results from one small group, but the data should be tracked and as teams improve, further scrutiny given to the results. But for now, when the games matter the most, curling should just play on. 

Episode 65 - John Ferguson

John Ferguson developed management skills from behind the tee-line.  Dealing with a contentious boardroom seemed easy after numerous years as vice for two of the most eccentric skips in curling history. As third for Paul Gowsell, John won the 1977 Canadian Juniors and 1978 Uniroyal World championships. He eventually teamed with Ed Lukowich and joined by Neil Houston and Brent Syme, they won the 1986 World Championship and captured the bronze medal at the 1988 Olympics in Calgary. John shares stories from across his curling days and gets to reminisce while watching a clip from Fast Eddy Curling Tips.

Check out the latest episode of Curling Legends Podcast

Episode 64 - Guy Hemmings

Guy Hemmings found curling by accident. Having moved to Montreal for University, during a Sunday morning walk he saw a sign to try curling at the Outremont Club. This chance encounter would eventually lead him to skip Quebec to the Brier finals. Twice. Guy, along with Pierre Charette, Guy Thibaudeau and Dale Ness, won over the crowds in Winnipeg (1998) and Edmonton (1999) with their play on the ice during the day and in the Patch each night. Guy shares his passion for the sport and describes what it's like being a celebrity in Western Canada while going unnoticed in your hometown.

Check out the latest episode of Curling Legends Podcast