The oft-used phrase “sophomore slump” seems to apply to a lot of professional athletes these days, which makes sense: the opposition has had an entire offseason to adjust after a rookie season, so teams coming into matchups against a player who were blind before are now armed with enough info to tear apart your gameplan.
So when Ryan Mountcastle started off slow this season, I figured it was because teams were attacking him differently. He would need time to reformulate his approach to at-bats. Maybe a couple weeks.

But that hasn’t been the case so far. Mountcastle is slumping pretty hard — he’s slashing .167/.208/.264 through 20 games and has just one home run thus far. Mountcastle is about to enter May as one of the least productive hitters in baseball. Here’s Mountcastle’s Statcast profile (right) to make it clear.
What’s changed? Why is Mountcastle struggling so much this season? Let’s attack that problem from a couple different angles.
Pitchers Aren’t Attacking Mountcastle Much Differently
Mountcastle saw fastballs 52.7 percent of the time in 2020 and he mashed, hitting .356 and slugging .492 against those pitches. Mountcastle saw breaking balls 35.4 percent of the time in 2020 and still found success, hitting .327 and slugging .442.
In terms of pitches seen, Mountcastle is seeing slightly more breaking balls and slightly fewer fastballs than last season. His fastball percentage has dipped to 49.1 and his breaking ball percentage has climbed from 35.4 to 39.4.