PHOENIX -- The bullpen holds some mystery for the A's this spring, but manager Bob Melvin expects right-hander Fautino De Los Santos to play a big role one way or another.

De Los Santos went 3-2 with a 4.32 ERA in 34 games as a rookie last season, notching 43 strikeouts in 33 1/3 innings.

"This is a big year for him," Melvin said. "We're not targeting him (for a specific role yet) ... But now there's a little bit more of target on him in that we expect big things out of him."

De Los Santos primarily needs to continue developing his slider to complement a high-90s fastball, Melvin said. But De Los Santos also must cut down walks and hold runners better.

Another reliever in camp, lefty Jordan Norberto, could also land a spot in the bullpen. He was acquired last season from Arizona in the Brad Ziegler trade but struggled with his command. Norberto worked as a starter in the Dominican Winter League this past offseason but has primarily been a reliever since 2008. Melvin mentioned the possibility of experimenting with Norberto as a starter in the minors if he doesn't make the big league club out of camp.

As for the A's rotation, it's shaping up to be right-handed heavy no matter who the five starters are. If Dallas Braden were to begin the season on the disabled list, Tom Milone is the only left-handed starting candidate currently in camp.

Melvin doesn't see it as a big issue. He said the five best pitchers will land in the rotation, and if it's five right-handers, so be it.