I think if he pitches smart and keeps the ball moving and down, he can account for the lack of velocity for three outs. He has been much better in outings that are less than six outs. the problem is I'm not sure theres is another option to look at. Maybe Burns? He's a little young, at one time Perez was new.
Motez accounts for over half of the teams error totals. SS might need to be looked at but I think the rest of the team has been ok, Villar is the only other Bull with more than one error and two of the three came in the opening series. Another three can be contributed to relief pitchers and situational players. Which only leaves two errors spread out among the remaining six positions, including a perfect backstop (huge). I just don't think defense will be a weakness, moving forward. At least I haven't seen the evidence of that yet.
Out of curiosity, where do you think he struggles defensively.
I don't know that he is a plus defender but, certainly serviceable enough for his bat.