Expected Goals (xG)

1. Definition: xG estimates the likelihood of a shot resulting in a goal based on factors like shot location, type, and context by assigning an xG value to each unblocked shot attempt. Different models will assess the danger of a single shot attempt differently.

2. Relevance: A good xG model correlates strongly with actual goals scored. It correlates highly with winning single games as well as winning and on a season level. This makes this a reliable indicator to measure the performance of a team or a player.

3. Actionability: There are typically more than 10 times of unblocked shot events than goals. Thereby xG can provide performance insights for smaller sample sizes of games or game situations. 

Other Shot Metrics

1. Definition

• Shots on Goal (S, aka Shots): Shots that hit the net.
• Fenwick (F): Unblocked shot attempts.
• Corsi (C): All shot attempts, both blocked and unblocked.

2. Relevance

• Shots, Fenwick, and Corsi correlate moderately with puck possession.
• On a season level Shots, Fenwick and Corsi correlates moderately with winning.

3. Actionability

• The offensive output of a team as well as the opponent output a team is giving up can be divided into volume (count of shots / fenwick / corsi) and average danger per shot.
• When trying to change the output a team can focus on changing the volume or changing the danger.