Note: All statistics used in this column are as of games ending May 15, 2011.
Conventional wisdom is that strong special-teams performance is important, especially in the playoffs. While special teams do drive results, accounting for nearly 25 percent of goals in just more than 10 percent of the ice time, short samples like the playoffs tend to leave us with more questions than answers. The main questions: How much of the performance was real or luck, and how much is it a predictor of future performance?
In regard to special teams, the answer to the second question is "not much."
There have been many studies on the consistency of performance in the different situations. JLikens at Objective NHL has shown that power-play success and penalty-kill success for individual teams correlate at .347 and .332 rates respectively over consecutive regular seasons, meaning they vary quite a bit from season to season.
The main reason for that is due to the high amount of random variation and luck affecting the results. As Gabe Desjardins has shown, random chance affects 38 percent of a team's total regular-season performance. Adjust that figure for the 10-plus percent of that ice time accounted for by special teams and the results become even more random and even less dictated by skill.
Take that same small proportion of playing time and shrink it to just the playoffs, a much smaller sample to look at, and the skill aspect of special teams just about goes out the window. Teams do have special-teams skill, but given the nature of the playoffs it's almost impossible to prove that a team's performance is anything besides good or bad luck. So, what does that mean for the remaining four teams in the playoffs? Well for starters, Boston Bruins fans shouldn't get too discouraged by their brutally underperforming power play.
To best assess how good the final four teams have been on special teams you have to remove the random chance factor from the equation. Therefore we can look at a statistical technique called regression to the mean to help factor out the randomness caused by the small sample. Take the special-teams rates in the playoffs for the four remaining clubs, regress them against the NHL average in the playoffs and you'll get an adjusted number that provides a slightly clearer picture of the teams' skill. To those unfamiliar with the concept, we're simply placing more weight on the actual performance and even more on the NHL average because those are the more usual results over a longer period of time, thus eliminating some of the luck that can produce fluke results. This won't completely give us a true talent number, but it is a much better indicator of exactly how well a team has performed.
Power Play 2010-11
Team Opportunities Actual PP Regressed PP
TBL 50 26.0% 19.4%
VAN 40 22.5% 18.9%
SJS 52 15.4% 17.6%
BOS 41 4.9% 15.7%
Penalty Kill 2010-11
Team Opportunities Actual PK Regressed PK
TBL 58 94.8% 84.6%
VAN 51 84.3% 82.0%
SJS 56 82.1% 81.8%
BOS 46 80.4% 81.2%
As you can see, there isn't much separation between the four special-teams units once you account for the small sample size. The penalty kill is basically a push; with the Lightning -- whose PK rate of 94.8 percent is the only truly striking figure -- only slightly outperforming the Bruins -- who killed just more than 80 percent of their penalties -- when you adjust for random chance.
The power play has a little more separation due to the hot play of Tampa and Vancouver while Boston has, well
struggled. But the impact is less than you may think.
Teams have averaged 3.92 power plays per game so far in the playoffs. So, assuming a series went seven games and that same number of power plays were awarded, the difference between Tampa Bay's adjusted power-play rate and San Jose's comes out to a grand total of
wait for it
zero goals. The difference between Boston and Tampa Bay's power-play rate over a seven game series is one goal. The difference between Boston and Tampa Bay's regressed penalty-kill rates over a seven game series also is one goal. So it seems the performance of special teams won't be the deciding factor if the Bolts blow by the B's. In fact, if the Bruins stick around long enough, expect their power play to bounce back big-time.
The lesson here is that hockey is won at even strength -- where team skill truly separates squads and how the majority of the game is played. The game of hockey is littered by luck and randomness that heavily influence a team's record over 82 games, never mind in a short playoff series.
A version of this story originally appeared at ESPN Insider .
Corey Pronman is an author of Hockey Prospectus.
You can contact Corey by clicking here or click here to see Corey's other articles.