Cullen: Shot differentials, save percentages for Round Two

Scott Cullen
5/14/2013 3:43:07 PM
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Before each round of the NHL Playoffs, I crunch a few basic numbers and come up with an expected goals for and against for each team, based on shot differentials and save percentages.

In the first round, the team with the higher expected goals, using these calculations, won seven of the eight series, with the Los Angeles Kings' win over the St. Louis Blues upsetting the bid for perfection.

Since I'm the first one to emphasize that overall statistics (or standings) are not necessarily representative of the current value for a team, especially with respect to injuries, these statistics merely provide a baseline for the series, perhaps providing an idea what a team needs to do in order to emerge victorious.

In some cases, teams will simply need to keep doing what they've been doing throughout the regular season; in others, they might need better goaltending, or fewer shots against, or more shots for -- just something -- to provide better expected results in a seven-game series.

The calculations below are simple and the expected goals for each team in the series are determined by taking each team's shots for and against over the course of the season and splitting the difference.

So, Chicago has 31.4 shots on goal per game through the regular season and first round of the playoffs and Detroit has allowed 28.1 shots on goal per game; the average of those two numbers is 29.8 shots, so that's the number that is then multiplied by (1 - the opposing goaltenders' save percentage) to determine an expected goals per game.

Finally, the number is multiplied by seven to indicate an expected goal total for a seven-game series. There's no guarantee that scoring more goals in a series will result in winning four games first, but the odds certainly favour the team that scores more.

Team SF SA Goaltender SV% Expected GF/Series
Chicago 31.4 26.4 Corey Crawford 0.930 16.45
Detroit 30.2 28.1 Jimmy Howard 0.921 13.87

Verdict: Naturally, the top-seeded Blackhawks are favoured and something will have to go differently for the Red Wings to pull off the upset. That hardly means it can't happen however. If Jimmy Howard outplays Corey Crawford in goal, that could be enough to swing the difference. If Pavel Datsyuk and Henrik Zetterberg raise their games and are more productive than Jonathan Toews and Patrick Kane, for example, that could be enough. Chicago might have more quality scoring options, but that's to be expected from the top seed and it's why they are likely to win.

Team SF SA Goaltender SV% Expected GF/Series
Los Angeles 29.3 25.5 Jonathan Quick 0.909 15.36
San Jose 32.2 29.2 Antti Niemi 0.925 18.38

Verdict: Jonathan Quick may ruin this model. He played very well (.944 SV%) in the first round after a subpar regular season. Should there be some concern that the Kings were outshot by 4.7 shots per game in Round One against St. Louis? Probably. The Blues play a stifling defensive style, that's a given, but the Kings didn't win the territorial battle as they did in the regular season while facing a Blues team that is the furthest thing from explosive offensively. From San Jose's perspective, they capitalized on power plays against Vancouver in Round One, scoring seven goals with the man advantage in four games. If the Sharks and Kings trade a similar number of chances, Niemi has been the steadier goalie over the full 2013 season but, if Quick is on, he can easily overcome these expectations. He's done it against St. Louis in each of the last two seasons (two series in which the Kings weren't given the edge) already.

Team SF SA Goaltender SV% Expected GF/Series
Pittsburgh 29.8 29.6 Tomas Vokoun 0.928 12.27
Ottawa 32.9 31.7 Craig Anderson 0.943 15.75

Verdict: Pittsburgh has such skill, and a potent power play (7-for-21 in Round One) that they finish a relatively high percentage of their shots on goal, a playoff-leading 15.0% in the first round (Ottawa was second at 13.0%). This after the Penguins finished second in the regular season (11.3%), when Ottawa ranked last (7.0%).

Part of the reason that I haven't included team shooting percentages in these calculations is that, at the team level, it's very difficult (if not impossible) to sustain any shooting percentage that is far removed from the average and there are so many moving parts to a lineup that it's hard to gauge the effect on percentages on a team level. Using goaltender save percentages is a different matter, however, since there is, ideally, one goaltender being used.

So, what we have in this series is a Penguins team that needs to maintain high shooting percentages and needs success on the power play to do so. On the other hand, a big reason why the Senators have enjoyed success this season is the play of Craig Anderson. Can Anderson continue stopping more than 94% of the shots he faces? That may be just as unrealistic as expecting the Penguins to score on 15% of their shots, as they did against the Islanders. Any team that gets goaltending at that level is going to be incredibly difficult to beat, but especially so if they also win the shot differential battle and the Penguins were outshot by 5.0 per game against the Islanders.

Essentially, the Penguins deserve to be favoured, but these numbers do indicate that there is reason to like the Senators' chances nonetheless.

Team SF SA Goaltender SV% Expected GF/Series
Boston 33.2 29.2 Tuukka Rask 0.928 15.38
N.Y. Rangers 30.7 28.7 Henrik Lundqvist 0.929 15.09

Verdict: Boston's expected shot differential, which has been a team strength for several seasons now, could take a hit if their defence doesn't get healthy. They survived the first round against Toronto with Andrew Ference and Dennis Seidenberg hurt late in the series, but that's no way to match up with the Rangers in the second round. Both goaltenders have been very good this season. While Lundqvist has a longer track record that might give him the edge, it would hardly come as a shock to have Rask match him save for save, given their performance over the last few seasons. These numbers suggest a slight edge to Boston, but slight enough that personnel differences (ie. injuries) could alter the expected outcome.


Scott Cullen can be reached at and followed on Twitter at  For more, check out TSN Fantasy Sports on Facebook.

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