DENVER -- The Chicago Cubs placed Mark Prior on the 15-day disabled list Saturday with shoulder tendinitis, a move that could mean an end to the right-hander's season.
Prior has been on the DL eight times in his four-year career in the majors, including three this season. The latest trip comes after he allowed five earned runs in three innings in an 8-6 loss to Milwaukee on Thursday.
Prior didn't feel anything wrong with the shoulder, but a loss in velocity in the third inning led the team to send him back to Chicago for an MRI on Friday, which showed rotator cuff tendinitis.
The Cubs want Prior to rest for three weeks before throwing again, which could mean the end of his season if he doesn't have time to make enough rehab starts before rejoining the Cubs.
"Everybody can do the math as to what that does for the rest of the season," Cubs trainer Mark O'Neal said. "At the end of the three weeks, hopefully we're going to [start] throwing and we'll go from there -- I haven't really looked at the calendar. Then it would take 10 days of bullpen to get going again. The likelihood of him returning this year is questionable."
Prior began the season on the DL with a sore shoulder and went back on in July with a strained oblique muscle. He's made nine starts, going 1-6 with a 7.21 ERA, his only win coming against Pittsburgh on Aug. 5, when he allowed five hits and two runs in 5 2/3 innings.
"I'm more disappointed for him," Cubs manager Dusty Baker said. "It's been a tough couple of years here, on and off the DL. He's not very happy about it."
The Cubs started the season with what was supposed to be a strong pitching staff with a rotation that included Prior, Kerry Wood, Greg Maddux and Carlos Zambrano. But Prior has had trouble staying healthy all season, Wood has been on the DL since June with a partially torn rotator cuff -- he opted against surgery last week -- and Maddux was traded to the Dodgers.
Zambrano is 12-5, though he's lost his last two starts after going 9-0 in June and July.
That's left the Cubs with no other choice than to start rookies like Rich Hill, Angel Guzman, who was recalled for the third time this season to replace Prior, and Sean Marshall. Chicago has had rookies start 45 games this season, second-most in the major leagues to Florida (63).
"The combination of young and inexperience, I've never had a staff that had so few innings in Triple-A and Double-A," Baker said. "Most have come up through the minors and had quite a few innings in them -- a year, year and a half maybe, and some time in Triple-A."