The only positive I see to starting Barney is that he's a plus defender (from everything I've heard). At the same time, there is no plus part of DeWitt's game. He's better offensively overall than Barney, but isn't particularly good either. Thus, since you're going with a young guy anyway, the reasoning would be to go with the guy that already features a plus skill and hope the other side comes around enough. Barney, it sounds like, is Theriot with much better defense and a slightly worse bat. That said, I'd prefer to go with DeWitt. Both are young but DeWitt has shown more offensive potential. With Aramis, Starlin and Pena around the infield, we have good to very good defense at 3 of 4 positions and can afford to put up with poor 2B defense with the hopes that DeWitt's bat comes around. There are plenty of good reasons to prefer DeWitt to Barney, but the makeup of the rest of the infield defense isn't one of them. If over the course of a season Barney's superior defense turns X additional balls in play into outs, then the run-value of that improvement is whatever it is, regardless of what anyone else on the field is doing. Well, the rest of the defense can fractionally help. If Ramirez, Casto, and Pena all had excellent range and Dewitt's main problem was a lack of range they could make that up with positioning. If Castro and Pena were both excellent at catching throws and DeWitt had issues with that then they could help in that regard. But I don't think either of those is particularly true so I don't think the rest of the Cubs defense would help DeWitt much.