I am no expert, but his defense seems to be in steady decline. Per Baseball Reference his Range Factor per 9 innings has gone from a high of 4.92 in 2013 down to an abysmal 3.26 in 2020. Yes, small sample size and all that, but it's well below league average. Like I said, I'm no expert, but this, couple with questions about ankle injuries (I don't know anything about them, only that there have been several) makes me concerned about his one calling card: defense.