We'll survive with Barney as a starter for a year if we don't have anyone better. What he did last year offensively (666 OPS) is BETTER than what could have been expected, given his minor league performances.
I would give him the job and let him play himself out of it, because he will continue to struggle with the bat in the majors. The real battle is between DeWitt and Cardenas. I think DeWitt has the best chance of the three of them of being an acceptable every day 2Bman. But the FO obviously doesn't view him that way, and the fact that he cleared waivers means that I'm in the minority on this one.
Cardenas could also be good, but he has to prove he can hit ML pitching, and it took him 2 1/2 years to figure out AAA pitching. Plus, his defense is average at best.
Long term, I see Barney as a utility infielder, because he doesn't have the bat to be a starter and he can actually play a solid shortstop.
Long term, I see Cardenas as a part time/platoon 2B-3B guy/pinch-hitter (kind of like a LH Jeff Baker). But he has a shot at becoming a good everday 2B, moreso that Barney. I would give Cardenas a 25-30% chance at becoming an average or better starter at 2B, and Barney a 5-10% chance. (And those numbers are probably a bit generous, for both of them)
The guy in the organization above the A-ball level who had the brightest future as an everyday 2B was LeMahieu. He looked bad in his debut, but he had been rushed to the bigs. If the Rox give him a whole year of AAA this year, he could turn out to be a good 2B in 2013.
Torreyes and DeVoss are a long way away, but both could move quickly. DeVoss has to prove that he can handle 2B defensively.
Edited 2/29/12 by SVAZCUB