Monday, November 28, 2011

Power Play Trends: Why We Shouldn't Focus on Merely Results

As I was watching the CSN-Philadelphia broadcast of the Coyotes/Flyers game on November 18, during a break in the action of the Flyers’ first Power Play the following chart was shown to the viewer, entitled “Special Teams Reversal.”

First 8 GamesLast 9 Games
Power Play27.5%9.3%
Penalty Kill82.9%90.2%

Presumably to reinforce play-by-play voice Jim Jackson’s comment at the beginning of the Flyers’ first man-advantage that the power play had been “struggling here of late,” I see a completely different trend when I look at the same numbers.

As Gabe Desjardins pointed out in this article, “The PP is all about directing shots on goal,” and I’m feeling daring enough to assert that the PK is all about preventing shots towards your own net. Looking at the Flyers’ shot rates per 60 minutes on special teams during the first 17 games once again thanks to JaredL, it becomes less surprising why such a reversal took place:

First 8 GamesLast 9 Games
PP SF/6050.740.7
PK SA/6039.439.6

As of today, if the Flyers were to sport 50.7 SF/60 on the PP, they would rank 12th in the NHL according to BTN and 40.7 would put them 28th. Their PK numbers would rank them 2nd in both occurrences. What is more, if we look at the shooting data from the same span we see another trend bolder than Jaromir Jagr’s Movember ‘stache:

Power Play

ShotsGoalsShooting %
First 8 Games531120.8
Last 9 Games4648.7
Total991515.2

Penalty Kill

ShotsGoalsSave %
First 8 Games437.837
Last 9 Games445.886
Total8712.862

In addition to their more potent shot-generating PP in the first 8 games, the Flyers were shooting at an unsustainably high rate and opposing goalies were stopping an unsustainably low number of shots. The numbers are more reasonable on the PK, though the Flyers’ opponents were still running a bit warm with their shooting. As the sample size began to grow, we see the Flyers’ shooting percentage come back down to Earth as their opponents began to stop a more reasonable number of shots. Philadelphia’s PK numbers also even out by a bit less of a margin as we might expect based on the unit’s consistency.

Though such a turnaround may be alarming to those who still choose to judge power play success based on results, the fact of the matter is that the Flyers PP of the first 8 games was merely a mirage. As the season rumbles along, expect the Flyers’ special teams to mirror the second half of CSN’s chart rather than the first.

2 comments:

  1. "I’m feeling daring enough to assert that the PK is all about preventing shots towards your own net."

    Teams do have a persistent ability to have a PK Sv% above or below average though (unlike PP Sh%), likely as a result of goaltender skill, and the spread in save percentages is at least as large as the spread in shot suppression skills. It may (or may not) be the case that the PK skaters' job is just to suppress shots, but the team's success will be driven at least as heavily by their talent for stopping those shots.

    ReplyDelete
  2. Fair point, Eric. Even those do have a tendency to even out in the long run, but you're right - the variance involved in a 200-300 shot sample for goalies can swing in the right direction like it did with Rinne last year.

    ReplyDelete