2. Triston Casas
Casas is a tremendous young hitter, and it’s been fun watching him make strides at the plate since his call-up last September.
Unfortunately, his fielding at first base has not improved at the same rate. In fact, FanGraphs rates him as the second-worst defender at 1B this season among qualified hitters, ahead of only Toronto’s Vladimir Guerrero Jr.
The main issue for Casas is his size. Listed at 6’5 and 244 pounds, he’s a big dude. That helps him hit for power, of course, but it also makes him painfully slow around the bag. He’s simply not quick enough to get to many balls hit his way.
The good news is that Casas is still young (23), so he has plenty of time to improve his defense. Albert Pujols is a recent example of a similarly big-bodied player whose defense improved dramatically as his career progressed. If Casas leans out a bit and keeps working on his fielding, his defense should improve a bit with time.
If it doesn’t, Boston can always just stick him at DH, but you’d typically rather have an older veteran in that spot instead of a rookie.