Power play and penalty killing is a big focus of importance for NHL teams, and it’s a big focus for a lot of handicappers as well. But are those statistics as useful in the NHL playoffs as they are in the regular season? Should they be handled differently in the postseason than they are in January? Let’s take a look.

Looking back at 2009-10 season doesn’t provide a statistically sound sample of the significance of penalty killing and power play percentages in the NHL, but it does serve to give us an idea. The results form this year are essentially consistent with what we could expect in other years as well.

In the regular season, seven of the top nine teams in power play percentage were playoff teams, and 11 of the top 13 penalty killing teams headed to the playoffs. (It’s also interesting to note that every playoff team except for Nashville and Colorado was either top nine in power play or top 13 in penalty killing, but only two – San Jose and Detroit – appeared on both lists, so balance isn’t important as long as you have strength in one and general competence in the other.)

In the playoffs the story is slightly different. Power play percentage doesn’t seem to be nearly as big of a factor. The top two power play teams in the playoffs failed to advance out of the first round. L.A. lost their first series despite scoring an incredible 10 power play goals in just 26 tries. The top four power play teams were all eliminated by the end of the second round. Whereas the link between power play performance in the regular season and overall success was high in the regular season it really wasn’t in the playoffs. Penalty killing is different, though. Three of the top four penalty killing teams made at least the third round, and both Stanley Cup finalists were in the top four. In general terms, then, it seems to be more important that a team can kill penalties than score on power plays if they want to succeed in the playoffs.

While that might seem interesting and useful, there are a few good reasons why special teams stats in general aren’t worth relying on as much in the playoffs as you might in the regular season:

Small sample size in playoffs – Over the regular season the percentages are calculated over 82 games, so by later in the season they give an accurate representation of what the team is actually capable of. A team that is eliminated in the first round of the playoffs plays no more than seven games, and often fewer. That sample size is too small to be accurate because a brief hot streak or cold spell can unduly affect the stats. It’s like in Major League Baseball – it’s far more impressive if a guy is hitting .390 in August than it is if he is doing it in April.

Familiarity – In the regular season you are playing a different opponent every game in most cases, so you have to adjust to the power play and penalty killing styles they apply in each game. When you play a team several times in a row, though, you can become more familiar with what they tend to do and how to respond to it. Familiarity tends to mean that the team that is better overall on the power play or penalty killing can start to find ways to further exert their strength. That familiarity disappears when the team moves on to the next series, so the overall numbers aren’t necessarily significant.

The hot goalie factor – Teams that succeed in the playoffs tend to have a goalie who is playing very well. Over a small sample size like the playoffs that hot goalie can have a big positve impact on his team’s penalty killing, and a negative one on his opponent’s power play percentage.

So, what does it all mean? Simply put, I don’t worry about penalty killing and power play performance in the playoffs at all. In the regular season I rely on it heavily – and increasingly as the season progresses. In the playoffs, though, I instead look at stats that could influence the performance in those areas, but which aren’t as prone to problems – things ike save percentage, shots per goal, and so on.