CHICAGO -- Mike Montgomery will return to the Cubs' rotation to sub for Jonathan Lester, who was placed on the 10-day disabled list on Friday with left shoulder fatigue.
Montgomery was 2-3 with a 5.13 ERA in eight starts in the first half of the season, and he has compiled a 2.57 ERA in 27 relief appearances. The lefty threw 61 pitches over 4 1/3 innings in relief of Lester on Thursday against the Reds. His last start was July 19 against the Braves, and his next start will most likely be Wednesday against the Reds.
After Montgomery's outing on Thursday, Cubs manager Joe Maddon gave the lefty a heads up that he would likely sub for Lester.

"The guy's got all kinds of tools in the tool box, but he doesn't know how to utilize them yet," Maddon said of Montgomery. "I think he's finally understanding the cutter, the curve, the changeup to go with the fastball. He's one of the guys who should never get wild with his fastball because his other pitches are so good -- he can throw them for a strike."
Montgomery has indicated he'd prefer starting, and Maddon knows that.
"It's just a matter of time and opportunity with him," Maddon said.
Cubs president of baseball operations Theo Epstein said the team won't look for another starter while Lester is sidelined. Lester was not expected to miss much time.
"We've expended a lot of prospect capital to make this team better," Epstein said. "We think it's just a start or two, and Mike Montgomery is more than capable of filling in. We're going to fill that vacancy internally and go from there."
Worth noting
• The Cubs' bullpen entered Friday ranked second in the National League with a 3.63 ERA, but it was also fourth in walks (194).
"We don't want that to be a big part of our identity," Epstein said of the walks. "We believe in throwing strikes. It's tough lately with the walks. It's not something anyone is trying to do -- it just happens. To get where we want to go, we need to lock it in. Every 'pen goes through ups and downs. In July, we had a really good month with the 'pen.
"These are our guys, and we know they'll lock it in and find the strike zone."
On Friday, the Cubs restocked the bullpen. Right-hander Justin Grimm was placed on the 10-day disabled list because of an infection in his right index finger. Lefty Rob Zastryzny and right-hander Felix Pena were recalled from Triple-A Iowa.
• Lester and pitching coach Chris Bosio exchanged a few words in the dugout after the left-hander exited from Thursday's game. Maddon preferred not to reveal details, but he said it had nothing to do with how the Cubs were playing behind Lester.
"They had their little discussion right there," Maddon said. "I heard there was a little bit of a thing. There's nothing going on right now."
Lester also said it was no big deal.
"I don't think it was a 'confrontation,'" Lester said. "Whatever is said between a coach and player or player and player in the dugout stays there. It's not [Bosio's] fault I gave up runs."
• Catcher Willson Contreras, on the disabled list with a right hamstring strain, played catch on the field on Friday for the first time since the injury. Contreras said he's feeling good, but the plan is to shut him down for at least two weeks. He went on the DL on Aug. 11.
• Reliever Koji Uehara threw a second bullpen session on Friday. He has been on the disabled list since Aug. 8 with a neck strain, and there is no timetable for his return.