Expected Saves

As part of a longer-term attempt to deconstruct expected goals into a variety of different, more granular and perhaps slightly more descriptive models, I’ve knocked together an expected save model today, and I thought I’d highlight some of the more interesting results out of it. Below is the data for this year’s Premier League, containing:

  • Total shots on target
  • Shots on target saved
  • Goals
  • Expected saves – the model’s prediction of how many SoT should have been kept out
  • Saves above expected – how a keeper’s actual numbers compare to their expected numbers
  • Difficulty – the average difficulty of shot the keeper faced (this is calculated as sum(1 - xs) / count(shots))
  • Rating – simply saves over expected saves to make it easier to compare keepers

I’ve ordered by saves above expected because it’s a more in your face than the rating.

Season Keeper Shots Saves Goals Expected Saves Saves Above Expected Average Difficulty Rating
2015 Jack Butland 47 37 10 32.76 4.24 30.30% 112.94%
2015 Alex McCarthy 34 29 5 26.28 2.72 22.70% 110.34%
2015 Petr Cech 41 33 8 30.49 2.51 25.63% 108.23%
2015 Hugo Lloris 31 26 5 23.80 2.20 23.24% 109.26%
2015 Heurelho Gomes 38 28 10 25.94 2.06 31.74% 107.94%
2015 Adrián San Miguel del Castillo 30 22 8 20.65 1.35 31.17% 106.53%
2015 Tim Howard 43 32 11 30.97 1.03 27.98% 103.32%
2015 David de Gea 23 17 6 16.05 0.95 30.22% 105.92%
2015 Darren Randolph 12 8 4 7.43 0.57 38.08% 107.67%
2015 Sergio Romero 10 7 3 6.47 0.53 35.33% 108.24%
2015 Thibaut Courtois 21 14 7 13.77 0.23 34.45% 101.71%
2015 Michel Vorm 1 1 0 0.86 0.14 14.06% 116.36%
2015 Kelvin Davis 7 5 2 4.87 0.13 30.43% 102.67%
2015 Lukasz Fabianski 36 27 9 26.91 0.09 25.26% 100.35%
2015 Carl Jenkinson 5 3 2 3.01 -0.01 39.79% 99.65%
2015 Joe Hart 16 12 4 12.18 -0.18 23.86% 98.50%
2015 Adam Federici 11 6 5 6.53 -0.53 40.67% 91.93%
2015 Boaz Myhill 42 31 11 31.61 -0.61 24.73% 98.06%
2015 Robert Elliot 5 3 2 3.81 -0.81 23.82% 78.76%
2015 Simon Mignolet 30 20 10 20.95 -0.95 30.17% 95.47%
2015 Wayne Hennessey 8 5 3 6.04 -1.04 24.48% 82.76%
2015 Tim Krul 49 33 16 34.61 -1.61 29.36% 95.34%
2015 Willy Caballero 8 4 4 5.74 -1.74 28.25% 69.69%
2015 Artur Boruc 24 12 12 14.03 -2.03 41.52% 85.50%
2015 John Ruddy 45 25 20 27.10 -2.10 39.79% 92.26%
2015 Asmir Begovic 32 19 13 21.21 -2.21 33.71% 89.57%
2015 Kasper Schmeichel 42 25 17 27.49 -2.49 34.55% 90.94%
2015 Costel Pantilimon 52 33 19 35.76 -2.76 31.22% 92.27%
2015 Maarten Stekelenburg 20 9 11 12.41 -3.41 37.95% 72.53%
2015 Brad Guzan 46 31 15 34.74 -3.74 24.48% 89.24%

Some brief observations:

  • It’ll be interesting to see who goes to Euro 2016 for England, Jack Butland and Alex McCarthy are both making a good case early in the season.
  • That said, Alex McCarthy has faced the easiest shots on average of any keeper in the league (save Michel Vorm, who has had only one save to make).
  • Hugo Lloris is performing above xS, but not so much that Tottenham’s 5 goals conceded is overly flattering. Lloris is another that’s right down there in the difficulty stakes, and it’ll be interesting to analyse over the coming weeks whether this is tame shot-making, or defensive organisation.
  • The Brad Guzan vs Marrten Stekelenburg comparison at the bottom is fascinating – imagine if Southampton allowed as many shots as Aston Villa.

It’s early in the season, and saves are easier to make than goals (I’m not saying goalkeepers are the bassists of football, just that they save more than they let in, and strikers miss more than they score), so as you’d expect, the model matches reality fairly well so far. We can see this if plot expected saves versus saves – above the line is good, below is bad, further to the top right are the leakiest defences, bottom left are mostly backup, although Darren Randolph and Sergio Romero seem to have done fine when called upon this year.

expected-saves

I’ll be keeping this updated through the season and I’ll surface anything interesting I find in the historical data or across Europe. In the meantime, please enjoy the consistently inconsistent Tim Howard:

Season Shots Saves Goals xS xSdiff Difficulty Rating
2010 141 97 44 99.48 -2.48 29.45% 97.51%
2011 133 94 39 93.39 0.61 29.78% 100.65%
2012 128 89 39 85.00 4.00 33.59% 104.71%
2013 152 115 37 109.83 5.17 27.74% 104.70%
2014 109 65 44 72.81 -7.81 33.20% 89.28%
2015 43 32 11 30.97 1.03 27.98% 103.32%
Expected Saves

8 thoughts on “Expected Saves

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