Shot quality
Statistical measure of shot goal probability, isolating goaltender performance.
In ice hockey analytics, shot quality refers to the likelihood that a particular shot will become a goal, calculated using variables like shot distance, shot type (such as a wrist shot, slapshot, or backhand), and the number of skaters each team has on the ice. This metric helps separate a goaltender's performance from the team's overall defense. By comparing the actual goals a goalie allows against the sum of shot quality values for every shot they face, analysts can evaluate that goalie relative to the league average.
For instance, if a wrist shot taken from 15 feet during even-strength play historically goes in 15% of the time, that shot gets a quality score of 0.15. If a goaltender faces ten such shots in a game, the expected goals against would be 1.5 (10 multiplied by 0.15). Comparing the actual goals allowed to that expected figure gives a measure of goaltending performance that is somewhat independent of the skaters on the ice.
The concept first appeared publicly in a paper by Alan Ryder of Hockey Analytics. Since then, it has been adopted in slightly different forms by several hockey blog analysts, including the Forechecker at On The Forecheck and JavaGeek at Hockey Numbers.
- First public presenter
- Alan Ryder of Hockey Analytics
- Example shot type
- wrist shot from 15 feet at even strength
- Example shot quality value
- 0.15
- Example expected goals for ten shots
- 1.5
- Notable analysts using concept
- the Forechecker at On The Forecheck, JavaGeek at Hockey Numbers
Lore & Background
The concept was first publicly presented in a paper by Alan Ryder of Hockey Analytics. It has since been utilized in slightly varying fashion by a number of blog-based hockey analysts such as the Forechecker at On The Forecheck, and JavaGeek at Hockey Numbers. The method assigns a numerical value to each shot based on factors like distance, shot type, and even-strength status, representing the likelihood of that shot becoming a goal.
Reader's Guide
Shot quality serves as a tool to evaluate goaltending performance by isolating it from the effects of other players on the ice. In practice, a goaltender's expected goals against are calculated by summing the shot quality values of all shots faced. For example, if a wrist shot from 15 feet at even strength has a shot quality of 0.15, a goaltender facing ten such shots would be expected to yield 1.5 goals. Comparing actual goals allowed to this expected figure yields a measure of goaltending performance that is somewhat independent of defensive play. The approach has been adopted by several blog-based analysts, though the article notes it is used in 'slightly varying fashion' by different practitioners, indicating no single standardized formula. Its significance lies in providing a more nuanced evaluation of goaltenders than raw save percentage, by accounting for the difficulty of shots faced.
Did You Know?
- Shot quality is based on factors including distance, shot type (wrist shot, slapshot, backhand), and number of players on the ice.
- A wrist shot from 15 feet at even strength was given as a theoretical example with a shot quality of 0.15.
- Blog-based analysts such as the Forechecker and JavaGeek have utilized the concept in slightly varying ways.
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