I agree in Center Field especially , range, is of utmost importance.
At that Lewis has poor range at Third Base and that may be one reason he is not in the outfield where it really, really counts.
Slow to get to the ball, thrown in with an eephus pitch, that leads to extra bases and runs scored.
Lewis' bat, if he is a good as he has shown glimmers of, will keep him in the game but unless his fielding improves, a bit, he may be sharing DH with some other gents a bit on, if one of the AAA rookies is as good as some think they are.