The offense / defense argument comes down to opportunity. The slickest, rangiest fielding SS doesn't get enough balls hit his way to offset a noodle bat. The lwts run value of single is about .45 runs. The best short stops crank out 50+ VORP seasons with regularity through their prime. That means, if Mr Noodle bat is going to equate their value while hitting at a replacement level, then he's going to have to get to 100+ more balls in the field --- don't see that happening.
This team has a lot of resources, they shouldn't have to endure settling for a player with demonstrated deficiencies. If he's truly spectacular in the field, and if he can hit league average-ish, that's one thing. If he comes up with boiled Barilla in his hands, it just won't suffice.