DENVER -- Just about the time the Chicago Cubs get someone off the disabled list, another goes on.
Zambrano (7-4) was scheduled to pitch against Colorado on Friday night, but was scratched 15 minutes before the game with stiffness in his lower back.
It's Zambrano's second trip to the disabled list this season. He was out in May with a left hamstring strain.
Zambrano is scheduled to have an MRI on Sunday.
"Hopefully what he has is not serious and he'll be all right in a couple of weeks," Cubs manager Lou Piniella said before the game Saturday night against Colorado.
To replace his spot on the roster, the Cubs recalled righty Jeff Stevens from Triple-A Iowa. Stevens is with the Cubs for a third time this season and will fill a middle-to-long relief role. In five relief appearances Stevens has a 2.84 ERA.
"He's done well. He's been up and down quite a few times in the past few weeks," Piniella said. "Seems like we get a player off the DL, we reciprocate and put one back on."
The Cubs may soon have another starting pitcher available.
Ted Lilly, who's been out since mid July with left shoulder inflammation, is scheduled to go out on a rehab assignment in the middle of next week. If all goes well, Piniella said Lilly might join the Cubs on their West Coast road swing that begins Aug. 17 in San Diego.
"I'm eager to get out there as soon as I can," Lilly said. "I think at the same time they're conscious of making sure that when I do come back I'm prepared to finish up the season strong."
Any extra pressure to return with Zambrano sidelined?
"I'm going to do what I can do," Lilly said. "Carlos is an important part of our ball club. We need him healthy. He's been someone that I think this organization's relied heavily on over the years ... That puts a little more emphasis on the workload that the other guys have to do to try to make up for losing a starter like that."
Taking Zambrano's place in the rotation will be righty Jeff Samardzija, who will start Wednesday against Philadelphia.
Samardzija pitched Friday night in relief of emergency starter Sean Marshall, giving up two runs in four innings.
"He could go six innings if he's pitching well," Piniella said. "I don't see any reason why he can't -- big, strong kid."
Zambrano has been bothered by the back for a little while. He went just three innings in his last start against Florida on Aug. 1, before departing with lower back stiffness.
Although injuries keep mounting for the Cubs -- a team in the thick of a divisional race -- Piniella refuses to read too much into it.
"You can't complain about it. You've got to go out and compete, regardless," Piniella said. "I said at the All-Star break: the secret for our ball club was to get healthy, stay healthy and score runs. I've said that, I cling to it."