Notes
Evergreen note: “Analytics” are not mere numbers. They’re models: ways of bridging practical (what happens on ice) and theoretical knowledge (what will or can happen based on prior events). They help define the conditions of performance over a period of time rather than glimpsing raw plus-minus. The climate versus the weather; defining the signatory rather than just the signature. These are not meant to be a right or wrong way to look at a hockey game; they’re meant to be useful in understanding the conditions of hockey itself.
The Stat: Evolving-Hockey’s goalie charts: Expected Fenwick Save Percentage (xFSv%), Fenwick Save Percentage (FSv%), Delta Fenwick Save Percentage (dFSv%), and expected goals above replacement per unblocked shot allowed (xGAR/FA).
The question EH’s goalie charts attempt to answer: If we assume league-average goaltending and account for team performance, how well does a goalie perform in proportion to the shots we should expect them to save?
How it answers that question: One of the biggest blindsights in analysis is goaltending. How do we distinguish between good goaltending and good defense? How do we know who’s really pulling the Goals Against strings?
Evolving-Hockey’s goalie cards break it down to the marrow. But first, a little clarification: Fenwick refers to an unblocked shot attempt. You might be wondering why they don’t use Corsi, which refers to a shot attempt. That’s because the NHL doesn’t actually track where a shot was taken if it were blocked. Hence why Fenwick is used. Now let’s look at our attachment for the day.
The first bar on the far left is the team’s expected save percentage versus unblocked shots allowed by the team (xFSv%). This gives us a broad view of goalies + team performance.
The second bar is unblocked shot save percentage (FSv%), which gives us a closer look at Oettinger’s performance on its own.
The third bar is difference between the first two bars (dFSv%), which shows us that Oettinger is not giving Dallas the saves that they probably deserve given what we should expect.
The last bar, or expected goals above replacement per unblocked shot allowed (xGAR/FA), is the bottom line: in this case, Oettinger is a deviation below the mean in proportion to what goals we should expect him to save.
“Okay what what is xGAR?”
xGAR refers to expected goals above replacement. GAR is essentially an attempt at a single-value stat. GAR models weigh the following variables against how much higher (or lower) a ‘player’ will perform over a replacement-level (average performance of a 13th forward or 7th defenseman) baseline.
Even Strength Offense
Even Strength Defense
Power Play Offense
Short Handed Defense
Penalties Taken
Penalties Drawn
The end result is a single number that can be represented via goals. You might be wondering what this has to do with teams? The same mathematical template is used to calculate team performance, but yes, it must be adjusted.
