A lot has been made of ‘expected’ stats permeating the baseball analytics landscape and how they do yeoman’s work to determing how good a player probably ‘should’ have been.
Expected Weighted On-Base Average (xwOBA), for instance, was put together to estimate how much offense you should have expected a batter to produce based on things like exit velocity, launch angle, and the player’s sprint speed. In other words, if they’re only hitting .210 with a 10.1% HR/FB rate but they’re smashing line drives over 100 mph off the bat all the time, you’d be considered very reasonable to suggest that they’ve simply been a bit unlucky and better times are right around the corner.