The Leafs Team Save Percentage vs. Pythagorean Winning Expectation

Long time reader first time caller mf37 is sort of like my muse. If I had to credit him every time he gave me an idea for a post or shoved me in the right direction you'd all probably tell me to save the time and just have him write here. We'll ignore that I dipped my toes into Leaf blogging because of his blog, Ninja's blog, the BoO and PPP's original home at Blogspot and get down to brass tacks.

One day after the trade deadline and as a collective group we're angry. We're frustrated and at wit's end and I think a lot of people are wondering how we ended up here. This season started off with a ton of hope and after a thrilling preseason this team fell off a cliff.

I decided to run some numbers to see where the Leafs would be in the standings if they had a better save percentage as a team. This doesn't place all of the blame on the goaltenders; clearly our defense and forwards hang them out to dry plenty. Clearly the object is to not get scored on as much as we do, but just how much would a better team save percentage change the 09-10 Leafs' fortune?

Exhibit A: Our four goaltender's raw numbers for all to see:

  SA GA Saves SV%
Giguere 137 12 125 0.912
Gustavsson 862 88 774 0.898
Toskala 676 85 591 0.874
MacDonald 157 17 140 0.892
Total 1832 202 1630 0.890

 

Oof. 0.890 is a horrible number. It would have been fine in the mid 80s but it's abyssmal now. Average NHL starting goaltending is in the .915 range now. We're looking to see how the Leafs would fare with a better team save percentage so we're going to use something called the pythagorean expectation which was popularized in baseball but can be summed up if you don't care about math as: the more a team scores relative to how many points it gives up the better it does. This is obvious.

Quick note: Jonas Gustavsson has allowed 3 more goals on 186 more shots than Toskala. That's how bad Toskala is.

I'm not mc79 or Gabe Desjardins, I'm not presenting the most fundamentally rigorous statistical analysis in the world here, but the first thing I did was using goals for and goals against calculate the pythagorean percentage for all 30 teams in the NHL. Then I compared their pythagorean percentage to their points percentage (Pts / (2 * Games played)) to determine if a correction factor was needed. I averaged a comparision of every team's PYTH% vs. their PTS% and got an average of 1.12 with a standard deviation of 0.05. That's a tight enough spread for me.

Here's a huge table of teams' records, goals for, goals against, etc.:


GP PTS GF GA Pyth Pts % Correction Factor
Washington  63 92 250 178 0.664 0.730 1.100
Chicago  63 89 207 153 0.647 0.706 1.092
San Jose  63 89 207 157 0.635 0.706 1.113
Los Angeles  62 80 190 167 0.564 0.645 1.144
Vancouver  63 80 204 158 0.625 0.635 1.016
New Jersey  62 79 166 147 0.560 0.637 1.137
Phoenix  64 79 169 163 0.518 0.617 1.191
Pittsburgh  63 78 198 181 0.545 0.619 1.136
Colorado  63 78 184 164 0.557 0.619 1.111
Ottawa  64 76 179 183 0.489 0.594 1.214
Buffalo  62 75 169 158 0.534 0.605 1.134
Nashville  62 73 174 176 0.494 0.589 1.191
Detroit  63 70 165 172 0.479 0.556 1.159
Philadelphia  62 69 190 169 0.558 0.556 0.997
Calgary  63 69 156 160 0.487 0.548 1.124
Dallas  62 68 176 191 0.459 0.548 1.194
Anaheim  63 67 180 193 0.465 0.532 1.143
St. Louis  63 67 168 174 0.482 0.532 1.102
Minnesota  62 66 175 178 0.492 0.532 1.083
Montreal  64 66 168 177 0.474 0.516 1.088
Boston  61 65 150 158 0.474 0.533 1.124
NY Rangers  63 65 165 170 0.485 0.516 1.063
Atlanta  61 64 186 196 0.474 0.525 1.107
Tampa Bay  62 63 162 189 0.424 0.508 1.200
Columbus  64 61 169 207 0.400 0.477 1.192
Islanders  63 60 164 197 0.409 0.476 1.163
Florida  63 60 164 185 0.440 0.476 1.082
Carolina  62 57 173 195 0.440 0.460 1.044
Toronto  62 49 163 213 0.369 0.395 1.070
Edmonton  63 44 158 220 0.340 0.349 1.026

 

So to get a team's expected points percentage we use this handy dandy formula:

PTS% = 1.12 * (Goals For)^2 / ( (Goals For)^2 + (Goals Against)^2)

Now we can play with that to see what would happen. If we raise the team's save percentage we lower the number of goals against and our PTS% formula will tell us what percentage of points we'll get.

SV% GF GA Pyth Pts Pct 82 Gm
0.89 163 213 0.369 0.414 67
0.895 163 192 0.418 0.468 75
0.9 163 183 0.442 0.495 80
0.905 163 174 0.467 0.523 84
0.91 163 165 0.494 0.554 89
0.915 163 156 0.523 0.586 94
0.92 163 147 0.553 0.619 100

 

We currently get terrible .890 goaltending. If we got .915 goaltending for 60 games from our starter and .905 goaltending for 22 games from our backup we'd be in the .913 range at the end of the year. That probably would have won us the eighth spot in a weak East.

I don't know how to fix our goal against trouble, it's continued despite a defensive overhaul, three goalies and two coaches but I do know that the Leafs should worry more about keeping the puck out of their net than anything else. As a parting note; if the Leafs finished with Vesa Toskala's 0.874 save percentage they'd be on pace for 60 points. Ouch.

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