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Friday, January 29, 2010

Notes from the BDO Grand Slam

A good weekend for Ontario Juniors taking home both the Mens and Womens national titles. You had to feel for the Manitoba skip watching in agony as his last rock just shaved past the Ontario stone. To make matters worse, the missed shot meant I lost a “Provincial” bet with Steven Lobel. Steve, your frozen Bison steaks will be in the mail next week. At least I have Alberta going against Ontario in the Brier for 10 in a row this year.

A non-curling stat I heard a lot these past few weeks was “92% of teams with +2 turnovers win play-offs game in the NFL”. I was hopeful the Minnesota Vikings would be one of the 8% and head to the Superbowl, but alas, it was not to be. Perhaps next year…

On to some Curling thoughts from the BDO.

1. Glenn Howard vs Pat Simmons

In the 5th end, Simmons is up 3-2 with hammer. It is Glenn’s last rock.

Howard is yellow

This is the last end of the Middle Game (middle three ends) and they are about to start the End Game (final three ends).

CBC announcer Mike Harris says Glenn can’t afford to leave the Simmons rock in play. Can he?

Hitting: Glenn is most likely going to give up a single to Pat. There is some chance he could make a hit and roll, in which case Pat will most likely try a double and then there is some chance he could miss or jam and Howard steals. Let’s estimate that Glenn makes a good hit and roll 20% of the time and Pat misses 25% when that happens, leaving the chance of a steal as 5%. There is also some slight chance of a blank, but we’ll assume those odds as negligible.

WP = (.2)(.95) + (.35)(.05) = 21%

Guard: If Howard elects to play a guard, he brings a deuce into play.

WP = .07x + .2y + .35z

Where x is the odds of a deuce, y is odds for a single and z is odds for a steal.

The Howard stone was just back tee-line and likely a single will occur often. Let’s estimate a single is 60% and odds of a deuce or steal are each 20%. WP = 20%. If we estimate the odds of a deuce to be lower, say 10% and set z =30%, WP = 23%.

What at first appeared to be a simple decision now appears to be very close and, depending on our assessment of the situation, perhaps in favour of throwing a guard. I personally preferred the hit, due to ice conditions and the Howard stone being behind the tee-line. If the rock is top button and/or the ice is straighter with less finish, I would prefer the guard in that situation.

6th End, Glenn is now trailing by 2 with the hammer and faces this with his first rock:

Richard Hart drew to the Open side with his last rock and Simmons hit and rolled just out of the rings. Glenn’s first instinct was to replace that stone and play the end out for a deuce and be tied up playing the 6th end without hammer. The Howard front end then talked him and Richard out of the shot, and they elected to play a freeze on their shot stone frozen to the Simmons rock in the four foot. Glenn asks “what are the odds of us getting 3? Brent responds with “zero if we go open”. Glenn then comments “we’re getting a guaranteed two if I go open”.

I disagree that the open side gives them a “guaranteed deuce”. There is some margin for error and if they don’t come deep enough Pat may have a possible hit and roll into the four to make Glenn’s last more difficult. The margin for error on the freeze is slightly higher and the result showed having 6 inches too much weight left Simmons a chance to get out of the end.

If Howard scores two, WP=33% or 2-1 (on the border of Close and Control, per my past article here If Howard makes a great shot, Pat still has a possible chance of running his rock in the top twelve into the Howard rocks and killing one, holding them to deuce. If Howard does score three, their WP = 67%, flipping the odds against Pat Simmons to 2-1 against. If Glenn is forced to one (the actual outcome) their chances drop to 14%.

WP = .14x + .33y + .67z = .33

The actual outcome that occurred was, I believe, the least likely. Glenn made the surprising mistake of being heavy. If he is light, even third shot, a deuce for Howard remains the most likely outcome. A little heavier and there may not have been a chance for the double by Pat, leaving a deuce possible. Glenn’s rock happened to land in the worst possible spot and I’d suspect this would happen perhaps 10% of the time. If we assume x=.1, how often does Howard need to score three to make this the correct call?

z = .05 or 5%

If we estimate the chance of scoring a single as 20%, then z doubles to 10% and it becomes a questionable call.

I like the call but not the execution. It was a shot which had very little margin for error and probably would result in a deuce anyway. If this is the 7th end, there is no question it is the correct call. Because it’s the 6th end there is some argument to taking the nearly “sure” deuce and 2-1 odds instead of risking 14%.

2. Kevin Martin vs Mike McEwen – Quarterfinal

In the 4th End, Martin is up 4-2 and McEwen has the hammer. John Morris hits the open BJ Neufeld stone in the 12 foot. On Neufeld’s next rock, thirds last for the McEwen team, they choose to hit and roll rather than draw. Martin then has an open hit when the roll is not made. Mike Harris points out that McEwen may then be unable to play behind the guard based if Kevin hits on the nose. As it turns out, Kevin rolls to the four foot and Mike has to hit.

Martin is Red

At this stage in the Middle Game, Mike has a 21% WP (Win Percentage) if the end is blanked and 38% WP if he can score two. Even if Mike is forced to 1, the WP = 21%. This stat clearly shows that there is no need to play for a blank as an option, there is no advantage to do so. If we add the fact they are playing Kevin Martin, the odds may be more in favour of attempting a deuce. Martin historically is 49-7 (87.5%) when 2 up without hammer and 4 ends to play. Mike could consider that Kevin’s numbers have come against teams weaker than his own. That is a factor he needs weigh against the baseline statistics to then estimate his teams’ likely chance of winning in this situation.

In any case, I prefer the draw on third’s last rock when it was available. Perhaps others might disagree.

After the blank in the 4th End, Mike has another draw opportunity in the 5th End and chooses instead to attempt a hit and roll on Neufeld’s first.

Mike Harris mentions that, especially on this ice, the draw is much higher percentage shot. I would agree.

In the 7th End, McEwen is behind 6-3 with hammer but after a jam on Kevin’s run-back attempt, is looking at scoring 3 and possibly even 4. Mike makes a draw around the corner guard to sit four and Kevin, as expected, attempts a double on the two open McEwen stones. Martin surprisingly noses the top rock leaving yellow sitting two.

Mike Harris states there is a double for four if he wants to attempt it. He does and misses, scoring only two. If McEwen simply draws for three, WP = 25%. Per earlier analysis, Mike may believe it to be even less, given his competition. If he is able to score 4, they would be 1 up without hammer playing the final end and WP = 60%. Interestingly, Martin is 12-20 or 37.5% when down 1 with hammer in the final end; very much in line with the average. Needless to say, the triple does not have to be made often for this to be the correct call. The miss, however, needs to be thick to get three and as is often the case. I’ll spare the reader the formula, but even if McEwen makes the same mistake 30% of the time and only gets the double 10%, it is still a break even decision.

3. Kevin Martin vs Thomas Ulsrud – Semi-Final.
In the 4th End, a surprising call by Kevin. Tied 2-2 with hammer, he is about to throw skip’s first rock.

Martin is yellow

To the surprise of many, including me, Mike, Joan and likely Ulsrud, Kevin elects to draw to the back four foot with the out-turn, rather than play a double. Harris comments that perhaps Kevin doesn’t feel the double is an easy shot. Martin may have also believed the top red likely jams on his own yellow and, with the swing in the ice and long guard, Ulsrud could be left with a possible hit to lay two. An interesting call which could have backfired if his rock was not placed perfectly. As it happened, Kevin and John then discussed the outcome and Kevin appeared to be more focused on the risk of Ulsrud tapping while John saw the possible chap and roll into the centre which would make it difficult for Martin to score. Was Kevin possibly so focused on one outcome that he missed seeing the other risks in his call? Unfortunately for Thomas, his final shot racked on the top red and left a draw for three.

4. Kevin Martin vs Glenn Howard – Final.
Mike Harris mentions during lead rocks that if Kevin Martin gets a deuce in the first end they are tough to beat. Are they ever! Kevin Martin is 80-6 (93%) since 2003 when up two without hammer and 7 ends remain. Glenn can at least take solace in the fact the last time Martin lost in this scenario was the BDO Final last year when his squad was able to overcome an 0-2 deficit against Martin.

In the 1st End, Glenn, without hammer, is faced with some options on his last shot.

Martin is yellow

Glenn elects to try and hit and roll in front of the yellow stone in the back eight foot. This would force Kevin to try a delicate hit for two or possible he may draw for one if the shot is perfect. Surprising that Glenn does not choose to play a soft hit and try to flop behind the centre guard, Joan mentions this is her preferred call. Another option is to simply try the thin double. I’m not sold on the shot that was called and prefer either the hit and roll inside (if it’s possible) or a freeze. The rock is right on the pin hole and a freeze will leave no draw for two. Depending on the location, Kevin may have a big weight double to remove his own shot stone, keep his shooter, and score two.
It’s possible Glenn was not entirely certain of ice and weight, being the first end. However, the hit and roll had, I suspect, had a similar margin for error if not more than the other options. Given Kevin’s record when 2 up and 7 more ends to play, I believe Howard would be better suited to look at all options, even those that may appear too aggressive for the first end of a game, even a Grand Slam final.
Further to this theory, when down 2-1 without hammer in the 3rd End, Richard Hart misses on a run-back on his first and John Morris splits the rings.

Rather than call a hit on Richard’s last, Glenn could have attempted a freeze and tried to escape the end. They instead try to roll to centre, to possibly set up a later attempt at a double on skips rocks. I believe the freeze was a better play, given the situation and score. Three down with 5 ends remaining WP=11% as an average and Kevin’s team is 67-3. On Glenn’s last shot he also elects to play a hit when a freeze may have been the more statistically correct call.
Incidentally, Glenn Howard is 87-12 when leading by 2 without hammer and 7 ends remain. No slouch either.

Some points in defense of Howard:
  • 25-23 (52.1%) when 2 down with hammer and 7 ends to play
  • 5-14 (26.3%) when down 3 with hammer and 5 ends remain. 
The question a team needs to ask is; given my strength vs the average team and my opponents strength versus the average team, and understanding these are small sample sizes, what will my outcome be against this opponent?  This answer involves adjusting the WP based on your team's ability and the strength of your opponent.  More on this in a future article.

Enough for tonight, I’m heading to sleep. Sweet dreams math fans. Mine are filled with nightmares of Favre throwing yet another play-off ending interception…..then I wake up and realize it wasn’t a dream.


  1. Always enjoy reading your blog Kevin. Hope you keep it up for many more years. Come say hi if you ever see me at one of the events, be fun to have a beer sometime and maybe I could justify some of our "statistically challenged" calls :)I think you get it right most of the time.
    Rich Hart

  2. Hey Kevin - Just discovered your blog after reading your column in the latest Curling News. My mathematically-inclined son was thrilled. This is way over my head, but I love the connection of math and curling - will be bringing it to the attention of my son's math teacher.

    Jean Mills

  3. Cool blog! May I suggest, when you use names in your examples, put the full first and last names at the top so we don't have to guess to try to match the first names to the last names if we are not familiar with the players. (=