We've talked about Chris Pronger's impact before, but here's an updated look at the data through the end of the season:
To explain: Corsi is a measure of how many shot attempts each team gets, and we reference it a lot because that correlates very strongly with possession, zone time, goals, and winning. In this case, I've plotted just Corsi in tied games, because score effects come into play otherwise -- regardless of who's controlling play, teams take a lot more shots when they are losing and desperate.
The difference Pronger has made this year is enormous; the Flyers got 54.1% of the shots in tied games when he was playing and 47.6% when he wasn't. In other words, with Pronger in the lineup, the Flyers played like Vancouver (whose Corsi tied was 54.2% as of JLikens' last tally) and without him they played like Ottawa (47.9%).
I can't imagine that full 6.5% bump is an accurate measure of his impact -- it's hard to believe that if we put Pronger on Ottawa they'd suddenly be Cup favorites. But even if his true impact is half that big, he's wildly underpaid and critically important to his team.
After the jump, a look into Buffalo's numbers: who gave them a boost, how big of a boost was it, and are they really as hot as we think?
The Buffalo Pronger
The Flyers aren't the only team in this series who got a big boost when they added a single player. Before acquiring Brad Boyes at the deadline, they had a very suspect Corsi tied of 48.4%. Since then, they are at 52.4%. Again, even if a lot of this is variance, that's great return on a second round pick.
Is Buffalo becoming a juggernaut?
It's probably not news to you that Buffalo has been playing better lately -- a lot of people are talking about how hot they are, with their recent 8-1-1 streak. It's actually been a season-long trend; the chart below shows that they've pretty steadily transitioned from getting badly outscored early in the year to dominating goal scoring recently.
That's a pretty scary looking chart, and we can see why the media is picking up on Buffalo's recent momentum as a story line and a basis for predicting an upset. We've already seen that recently they've gotten better at controlling the play and winning the shot battle, but that doesn't explain a continuous increase of this magnitude. What else has gone into their recent success?
Regression to the mean is our friend
Getting more shots than your opponents do is only one part of outscoring them. You also need those shots to go in, of course. Here's how Buffalo and their opponents have done in that regard:
As a reminder, there is a substantial amount of random variation in shooting percentages, even over a seemingly large 82-game sample, so the analytical community tends to regard those fluctuations as not having a lot of value for predicting the future. I know that's counter-intuitive, but if you think recent performance and momentum are valuable for making predictions, cover up everything after game 20 and ask yourself what predictions you would have made for the season at that point. Ryan Miller was performing terribly and the shooters were below average, and you would have concluded that the season was lost.
Just like Miller's horrible first 20 games didn't mean he was going to have a terrible year, his fantastic last 20 don't mean he's going to dominate the playoffs. Yesterday is in the past and tomorrow is a new day; the most likely result in the future is that he will perform near his career average.
The Sabres' momentum is a natural story line for the media to pick up. The goal scoring trend suggests that they're becoming an unstoppable behemoth, but that's not really true. They have been playing well lately, but the trend is markedly overemphasized by shooting percentage luck that we shouldn't expect to continue going forwards.
Head to head matchups
Finally, let's take a look at what happened in the teams' previous meetings. The Flyers got 52.2% of the shot attempts when the two teams faced each other this year, despite the score effect headwind created by their 14-10 advantage in goals.
Admittedly, three of those games were with Pronger and without Boyes, but in game 81 Buffalo had everything going for them: Boyes in, Pronger out, home ice, a playoff spot on the line, a reeling Flyers team. Buffalo did come away with the win, but the Flyers controlled the game, getting 54% of the shot attempts and 56% of the scoring chances, despite the score effects in a game where the Flyers led for almost 32 minutes and trailed for only 3.
Buffalo is a solid team. They absolutely earned their playoff spot and are perfectly capable of beating anyone in a short series. But if the Flyers have a healthy Pronger -- and that's a big if -- then they should be the better team.