Over the course of a season, a hitter's performance usually balances out. Everyone will go through hot and cold streaks, but in the end you'd expect that the numbers a hitter puts up will be representative of his true talent level. However, that's not always the case. Whether due to park effects, the quality of the opposing defense or just random variation, there will be some hitters who produce much more or less than what they -- or their teams -- expect.
Using data that Baseball Info Solutions collects, we can better understand who these hitters are. Our defense-independent batting statistics (DIBS) are able to give expected results on every ball in play for a hitter by comparing the ball's trajectory, direction and velocity to other similar batted balls and assigning value based on those results. We have found through extensive research that these expected numbers are more indicative of a player's future performance than his actual results, which is why we can use them to determine who's been lucky or unlucky.
By adding together all of a hitter's batted balls for a season, we can calculate his expected weighted on-base average (wOBA), comparing that to his actual wOBA. I chose wOBA over other metrics because of its accuracy. Using on-base plus slugging (OPS) would have provided similar results, but wOBA weights each type of hit relative to its run value and therefore presents a more accurate understanding of a player's skill. It's also on the same scale as OBP, which makes it more intuitive to use (league-average wOBA this season is .321).
Below, I list a few hitters who have seen some of the most extreme discrepancies between their actual and expected stats.