Giving reps at SS to the guy with the higher upside but who still has questions about whether he can stick at short, plus adding positional flexibility for the other guy? Just a guess. Vielma was playing 2B in Florida the week I was there, too. As with Polanco, fulltime duty at 2B at one minor league stop doesn't close the door on shortstop. If it were me, I'd give him (some more) time at 3B too. / edit - I took a look, and the guy who played 3B last night, Ryan Walker, has been mostly a second baseman in his career. Maybe the new regime is emphasizing positional flexibility a little more?