The ace of the staff is veteran righty Yovani Gallardo, who's still just 26 and has been a reliable, durable starter for four years, with 127 starts over that time. After him, though, no other rotation candidate has made more than the 63 career starts by lefty Chris Narveson, who just so happened to miss all of last season with injury.
The other four names in the mix are Marco Estrada, who has already been pegged as the club's No. 2, along with Mike Fiers and prospects Wily Peralta and Mark Rogers. As Tom Haudricourt of the Journal Sentinel writes, Rogers has an advantage in that he's out of minor league options, so he'll almost certainly break camp with the Brewers -- and most likely as a member of the five-man, as long as he doesn't pitch terribly in the spring.
While Narveson may be behind the curve because of a lost 2012, his advantage is that he's the only southpaw of the bunch. Fiers, meanwhile, succeeded in his first real shot in 2012, posting a 3.74 ERA and 1.26 WHIP. Peralta, then, could be on the outside looking in, as he has the least big league experience (five starts), but he's also considered the team's top prospect.
Spring training performances will go a long way toward determining which one of these pitchers will either shift to a bullpen role or possibly be sent to Triple-A until a need arises. Peralta, in particular, needs a strong showing, since he still has minor league options remaining and would be best served starting on a regular basis in the minors rather than sticking with the big league club as a reliever.