In his first full Major League season, the right-hander appeared in 55 games, compiling a 2.95 ERA. His career has been slowed by elbow and shoulder injuries, and the current inflammation is located on his side, just under his armpit.
"By the time we could get him ready, I think the season will run its course," Piniella said. "He's pitched in 50 some games, he's had a good year. Let's get him some good rest over the winter and get him ready for Spring Training next year."
Guzman had hoped to do more this year.
"I'm happy," Guzman said. "But at the same time, I'm not satisfied. I set some goals to achieve."
And next season? Guzman says his goal is to appear in 70-75 games.
"He's had a good season," Piniella said. "Hopefully, this is the beginning of him staying healthy for an entire season because he has shown that when he's right he can pitch and help a baseball team. Fifty-some games this year, hopefully a little more of a load next year."
The Cubs have tweaked the rotation for the upcoming series against the San Francisco Giants. Ryan Dempster and Carlos Zambrano will start Thursday and Friday, with Tom Gorzelanny going Saturday and Ted Lilly on Sunday. Lilly was skipped from Wednesday's start because of tendinitis in his left shoulder, but he threw on the side Tuesday at Miller Park.
"I think it's more of a cautious thing than anything else," Lilly said. "It's one of those things. We're in September, and there's no reason now to push it or take unnecessary risks."
Rookie Randy Wells is penciled in for one more start in the makeup doubleheader Sept. 30 against Pittsburgh, while Rich Harden is not in the schedule yet. Harden has been limited to throwing off flat ground and will throw a bullpen session on Wednesday. The Cubs would like to give him another start as well before the season ends.
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.