written by – Rangers Report
Using statistical analysis to evaluate goalkeepers is a work in progress, largely because not all saves are equal. Some shots are easier to save then others, so using simple save percentage isn’t always the best measure of a goalie’s success. Followers of the blog will know that we have been using Expected Goals Allowed to determine which goalies are allowing more or less goals then the projections suggest that they should. So far this season, according to Goals Minus Expected Goals – Mark Oxley (Hibs), Jamie Langfield (St. Mirren) & Wes Foderingham have been the best performers.
However, the purpose of this post is to see how much impact their team’s defence is having on goalie’s success. Are teams creating an environment that allows keepers to make mostly ‘easy’ saves or are they setting up the keeper to fail given the high rate of difficult shots that they face. In a recent post evaluating team defences, we described what constitutes a High/Very High Danger shot & what types of shots are classified as Low Danger Shots.
Below are the stats for the Scottish Championship goalkeepers who have have played the majority of minutes for their teams. They are ranked by save percentage (Saves/Shots on Target faced). Also listed is the percentage of shots on target faced that have come from High/Very High Danger areas.
|Goalkeeper||Team||Total Shots on Target Faced||Sv%||% HD/VHD SoT|
|Jamie Langfield||St. Mirren||33||0.818||0.53|
|Keith Cuthbert||Raith Rovers||38||0.789||0.47|
|Robbie Thomson||Queen of the South||34||0.676||0.59|
|David Crawford||Alloa Athletic||33||0.606||0.52|
This is proof of why simply ranking goalies by save percentage is not effective. Keith Cuthbert & Wes Foderingham have identical save percentages, but who has been called upon to make more difficult saves? Mark Brown & Danny Rogers have nearly identical save percentages but which of the two clearly should be doing better?
This graph may help visibly show which keepers are victims of their defensive shot environment & who are thriving in difficult circumstances.
- The blank bubble near the heart of the graph represents the league average in save% & in the percentage of shots coming from High/Very High Danger areas (0.724 Sv% & 0.50 HD/VHD SoT).
- The two keepers in the upper-right part of the graph, Jamie Langfield & Mark Oxley, have performed the best this season given their high Sv% & that the majority of shots that they have faced are coming from the heart of the goal area. Just imagine how much worse St. Mirren would be without Langfield’s strong play this season.
- The lower-right keepers are performing as expected. They have good Sv%s & given that their defences are limiting the percentage of dangerous shots that they are facing. They are having good seasons so far & a large part of that is the defensive play in front of them.
- The large cluster of keepers in the upper left represent keepers who are struggling, largely because their defences are allowing quality scoring chances. Sometimes a keeper ‘needs to make a save’ & Robbie Thomson & Danny Rogers are too an extent, but not to the extent of Langfield & Oxley.
- Then there’s Dumbarton’s Mark Brown. His defence has done an excellent job of limiting quality scoring chances but he has among the league’s worst save percentages. Compare Brown’s play to Morton’s Derek Gaston. If Brown’s stats were closer to Gaston’s then you may see Dumbarton higher up the league table.
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