CHICAGO (AP) The Chicago Cubs got an encouraging report on Jon Lester before placing the ace left-hander on the 10-day disabled list on Friday.
Lester was examined by team physician Dr. Stephen Gryzlo after he left Chicago's 13-10 loss to Cincinnati on Thursday in the second inning. He was diagnosed with tightness in his left lat and general shoulder fatigue, but his shoulder and side were deemed structurally sound.
''I think the big thing is just the overall performance was not there,'' Lester said. ''This is something that we tried to manage and get through. It just got to a point where you're doing a disservice to your team by going out there and not being able to perform.
''You feel like you can't help (going on the DL), but at the same time I wasn't helping out there. Let's get this thing right and get back to being myself.''
The Cubs are hoping rest will clear up both issues and Lester will be able to return not long after he becomes eligible.
''Let's just give him a break right now,'' manager Joe Maddon said before Chicago's 7-4 win in the series opener against Toronto. ''He's on board with everything. We're pretty sure it's going to be a minimal kind of a stay.''
Reliever Justin Grimm also was placed on the DL with an infection in his right index finger. Pitchers Felix Pena and Rob Zastryzny were recalled from Triple-A Iowa.
Grimm got the loss in the series finale against the Reds, allowing rookie Phillip Ervin's tiebreaking two-run homer in the seventh inning. The right-hander is 1-2 with a 5.40 ERA in 39 games this year.
Lester is 8-7 with a 4.37 ERA this season. He made at least 32 starts and pitched at least 202 2/3 innings in each of the previous five years.
''The guy gets out there all the time pretty hard,'' Maddon said. `He's kind of been our rock for a couple years now.''
Maddon believes the workload is responsible for the lat tightness and shoulder fatigue - and why Lester was rocked for seven earned runs in 1 2/3 innings on Thursday.
''I mentioned it after the game, I just didn't see any finish on the pitches,'' Maddon said. ''That's what he's talking about, he just can't get out there to finish his pitches right now. That's the difference between an 84, 85-mph cutter and an 89, 90-mph cutter. That couple miles an hour difference can make a difference.''
Mike Montgomery will step into the rotation while Lester is out. The versatile lefty is 3-6 with a 3.64 ERA in 35 games this year, including eight starts.
''I don't want to see anybody get hurt, especially our ace, but it's a challenge,'' Montgomery said. ''I feel like I can do it. I'm hoping he'll be all right.''
Zastryzny has appeared in one game for Chicago this season, allowing three runs in four innings. Pena is 1-0 with a 4.50 ERA in 10 games for the Cubs this season.