He lacks range, too. Little speed, slow breaks, but it seems like he usually takes the right route, but yes, dropping easy fly outs is not good.
What's the Sox record for errors by a RF'er?
Here are his fangraph ratings in RF:
0 DRS (thanks to his arm)
-1.2 UZR/150
+2.1 ARM
-1.0 RngR
-1.7 ErrR
Career
+13 DRS
-0.5 UZR/150
+7.3 ARM
-1.6 RngR
-6.1 ErrR
He only has 41 innings in CF
Career, he's a plus in LF: (954 innings)
-1 DRS
1.1 UZR/150
He must be close.