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Monday, February 08, 2010
That onside kick to open the 2nd half
I’m the biggest champion of WPA (win probability added) and WE (win expectancy) that there is. This is why I just love all the work that Brian Burke does. I couldn’t wait to read what he had to say about it:
Onside kicks are surprisingly successful when they are not expected. Since 2000, slightly over 60% of unexpected onside kicks have been recovered by the kicking team. An analysis based on Expected Points suggests teams should occasionally attempt surprise onside kicks if they believe their chances of recovery exceed 42%. Let’s also take a look at what WP would say.
In this case, the Saints were down by 4 points. A deep kick would typically give the Colts a 1st and 10 near their own 30, worth 0.32 WP to the Saints. A failed onside kick gives the Colts a 1st down at the Saints’ 40 or so, worth 0.26 WP to the Saints. A successful recovery gives the Saints possession at their own 40, worth 0.39 WP. In total, the onside attempt is worth:
0.60 * 0.39 + (1-0.60) * 0.27 = 0.34 WP
The onside attempt was a good gamble according to the numbers, but not by much--0.34 vs 0.32 WP. it paid off, and the Saints capitalized with a TD drive to take the lead for the first time in the game.
Or, another way to say it is: what IS the break-even point for recovery? Using those numbers, the win expectancy model ALSO says the breakeven point is 42%. Up until a point, using a point or run model is almost as good as using a win model. In baseball, you can safely do so all the way through the 7th, even 8th innings. So, I would suspect in football, you’d be safe up until the last 5 or 6 minutes of the game.
So, I disagree with Brian’s conclusion that it’s “not much”. .02 wins is very much alot, relative to everything else that goes on. If the breakeven point is 42% and the observed actual in those situations is 60%, then there is a huge market inefficiency going on here. A “surprise” onside kick is a great strategy. Of course, the classification of something being surprise is going to change alot once the receiving team starts to expect an onside kick.
I have the same issue with people who say that .02 wins is not alot in baseball. A great pitcher would be say a .680 pitcher, or +.180 wins above average per 9 IP. That’s +.02 wins per IP. So, is it a big deal if Halladay or an average pitcher pitches one inning? Well, I think it’s big. The actual number is +.02 wins. So, that means that .02 wins IS big. At the same time, an extra walk in an inning is +.03 wins. So, if you are upset if Halladay is taken out one inning early, you need to be furious when you have an extra walk in an inning.
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