Rebound shots have already been proven to have a higher conversion rate, so a goaltender who can absorb shots or direct pucks over the glass and into the corners creates a greater chance for defensively independent success than one who spits rebounds back into the slot.
If a goaltender generates more rebounds, but faces less rebound shots, it could be placed in the category of a goaltender-dependent advantage – one completely independent from an individual skillset.
Ultimately I want to assess how important this aspect is and its tangible impact on save percentage.
VALUE OF GOALTENDERS REBOUND CONTROL
Rebound control is an overrated skill.
most non-save goalie skills are overrated: Because the rest of the team can compensate for it.
Despite the focus on rebounds, there really aren’t that many rebound shots per game. This season there have been just 1.43 rebound shots against per team per game. Not only are the totals low, but there is not a whole lot of difference between teams in rebounds allowed.
A better measure of rebound prevention is the percentage of shots against that are rebound shots.
a gap of 2.5%, which is a typical gap between the best and the worst in any given season.
Once you include that in the equation, there likely isn’t a whole lot of margin left.
One of the reasons that we don’t see a lot of difference in things like rebound control at the NHL level is that goalies with particularly bad skills in that area would never make it there in the first place. However, we still need to be particularly careful to avoid making the mistake of letting the obvious nature of rebound control overly influence our evaluation of a goalie.
DO GOALIES HAVE ABILITY TO CONTROL REBOUNDS
Yet that skill is, likely, mostly unrelated to the “bigger” things in the game, like controlling shots or simply being a better player.
rebound generation is a team skill on the offensive level, and more of an individual goalie skill on the defensive level. In other words, individual skaters cannot generate many more rebounds, necessarily, but a team-wide offensive strategy or system can.
Goaltenders do seem able to control rebounds more than shooters can produce them, which only seems natural.
CAN GOALIES CONTROL NUMBER OF REBOUNDS
Rebounds account for 11% of all shots taken within 60 seconds of the previous shot, but 34% of the goals.
In general, outside of a few cases, goalies do not have an ability to control rebounds.
The regression is severe for the top group: more than 70% of the way towards the average for Group 1, which is part of the reason that I don’t think goalies can really suppress rebounds that much.
The best way to predict their Year 2 rebound rate is simply to guess that they’ll be league-average.
There isn’t that much a goalie can do in a given year to suggest he has the ability to save more than a few goals.
MEASURING REBOUND CONTROL
The ability to freeze the puck doesn’t seem to be a huge determinant of team success.
· First, while rebounds are undoubtedly more dangerous shots, they result in a shot attempt so rarely that they play a relatively smaller role in the overall results.
· Second, inevitably each frozen puck results in a defensive zone draw, putting the goalie at an immediate disadvantage, and potentially counteracting some of the benefit of preventing a rebound
GAME THEORY – REBOUND CONTROL
(Dec 2017)
preventing rebounds is not a highly repeatability skill,
my solution was to create an expected rebounds model using the same framework used to develop an expected goal models. The goal is the same, compare observed goals and rebounds relative to what we would expect a league average goaltender might surrender controlling for as much as we can.
shots goalies face are largely out of their control
However, goalies can assert some control over rebounds. How much and if this makes a difference is something we will explore.
Rebounds account for about 3.2% of all shots, but 13% of total expected goals. This ratio of rebounds being about 4 times as dangerous is supported by observed data as well. Shooting percentage on rebounds is about 27%, while it is 5.8% on original shots.
Looking at intra-goalie performance correlation supports the idea that making saves on rebounds is a less repeatable skill than the original shots.
While there is some repeatable skill, its not enough to treat any goalies differently in our model post-rebound due to remarkable ability (or inability) to make saves on rebounds.
Rebounds, particularly in expected goals models, can confound goaltender analysis by crediting goaltenders disproportionately for chances that they have some control over
Initial testing suggest that rebound adjustment adds incremental predictive power enough to justify it inclusion in advanced goaltending analysis where the goal is to measure goaltender performance independent of team defense with the publicly data available.
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