Andrew Cashner to begin rehab

PITTSBURGH -- Pitcher Andrew Cashner returned to the Chicago Cubs on Monday to begin his rehabilitation as he attempts to come back from two rotator cuff strains that have sidelined him for most of the season.

After throwing 20 pitches off the mound in Mesa, Ariz., on Saturday, his first time on the mound in more than two months, Cashner said he threw about 25 pitches on Monday in Pittsburgh.

"Today was my second bullpen. I've been throwing all three pitches with no pain," Cashner said. "I've just been working through some rust letting the ball go. I'll have another bullpen session on Thursday and we'll see where we're at."

Cashner, a first-round pick of the Cubs in 2008 who was considered their top pitching prospect last season, first strained his rotator cuff on April 5 in his first start of the season. The Cubs put him on the 15-day disabled list on April 8. During his rehab, Cashner re-injured the same shoulder during a bullpen session on May 16.

The Cubs will be cautious with Cashner this time around and will probably just let him go one or two innings at a time as he regains the strength in his shoulder. A month might be enough time for him to get back to the majors and pitch out of the Cubs bullpen in September.

"I think four weeks is a little too long. I believe my goal is two to three weeks to be back," Cashner said. "I think that's realistic, but I'm not putting any timetable on it. We'll just see how my shoulder feels."

A closer at TCU and a reliever with the Cubs as a rookie in 2010, Cashner was converted to a starter in spring training.

Bruce Levine covers the Cubs for ESPNChicago.com and ESPN 1000.