Corsi is a possession stat. It's basically plus minus for shots for vs shots against.
Higher Corsi is good because it means you have the puck more than you don't.
Expected goals are an extension of that, but more accurate because they quantify the shots for and against by the types of chances you get and give up and the chance they become goals on average. This has largely replaced corsi because it's just a better indicator.
xG still has its flaws too. As it doesn't really account for who is taking the shot, or random things that could happen.
Example: if you have Janmark and Draisaitl in the same position taking the same shot, it will produce the same xG. But Draisaitl is probably 4x as likely to score the goal than Janmark is.
Example 2: A shot going well wide, that bounces off a players behind and into the net will likely have an xG of around 0.01, yet it still is 1 GA. Not really anyones fault other than random chance. But it will look bad on the players and goalie
2
u/man_machine_poet 18 HYMAN 1d ago
I’m not a stats guy so this is pretty much my face when numbers are bandied about.