Expected Outcome stats help to remove defense and ballpark from the equation to express the skill shown at the
moment of batted ball contact. By looking at the exit velocity and launch angle of each batted ball,
a Hit Probability is assigned based on the outcomes of comparable historic balls in play.
By accumulating the expected outcomes of each batted ball with actual strikeouts, walks and hit by pitches,
Expected Batting Average (xBA),
Expected Slugging (xSLG), and (most importantly)
Expected Weighted On-Base Average (xwOBA)
tell the story of a player's season based on quality of and amount of contact, not outcomes.