CHICAGO -- Mike Montgomery is creating all sorts of intriguing questions for the Chicago Cubs.

Montgomery pitched six-hit ball into the eighth inning and helped himself at the plate, leading the Cubs to a 6-1 victory over the Pittsburgh Pirates on Monday night.

Montgomery struck out four and walked none in his second start since he was inserted into the rotation after Jon Lester was placed on the 10-day disabled list. The left-hander was pulled after Jordy Mercer snapped his 17 1/3-inning scoreless streak with a leadoff homer in the eighth.

"When he gets better counts and he's putting the ball on the ground, he's tough," Cubs manager Joe Maddon said, "and I think it begins with the better counts. He did a nice job getting ahead."

With Lester nearing a return, Montgomery (5-6) could be headed back to the bullpen. The Cubs also could decide to move slowly with Lester and give Montgomery another start, or Maddon and company could go with a six-man rotation to provide more rest for their pitchers.

Montgomery also is up to a career-high 109 1/3 innings, which could factor into the Cubs' plans. For now, he said he is moving forward as if he is going to start again.

"That's going to be kind of my routine, and if it changes, it changes and I'll be able to adjust from there," he said.

Carl Edwards Jr. got three outs before Wade Davis finished the six-hitter as Chicago moved 2 1/2 games ahead of idle Milwaukee for the top spot in the NL Central.

Trevor Williams (5-7) hung in there with Montgomery, pitching five innings of two-run ball, but Pittsburgh lost for the 11th time in its last 16 games. Mercer went 3 for 3, David Freese had two hits and Andrew McCutchen singled for the Pirates.

"Montgomery threw a hell of a game," Williams said. "It's one of those nights that you tip your cap to him."

Chicago was clinging to a 1-0 lead when Montgomery beat out an infield chopper over Williams' head for a leadoff single in the fifth. He advanced to third on Tommy La Stella's one-out single and scored when Anthony Rizzo's bases-loaded drive pushed McCutchen all the way back to the wall in center for a leaping catch.

The Cubs added three more in the seventh on Alex Avila's bases-loaded infield single and errors on second baseman Sean Rodriguez and catcher Chris Stewart. Rodriguez threw wide of first while trying to retire Avila, and Stewart threw the ball into center field to bring home another run.

"We weren't able to create much offense," Pirates manager Clint Hurdle said. "Trevor pitched a very gritty game, a gutsy game. We put ourselves in a position to be in a closer game and we couldn't get outs when we needed to."

QUITE A SHOW

Cubs shortstop Javier Baez made a pair of nice defensive plays. First, he robbed Jose Osuna of a hit with a terrific diving stop and strong throw in the third. Then he made a diving catch in the fifth and got up to tag Mercer for an unassisted double play.

TRAINER'S ROOM

Pirates: INF Adam Frazier was placed on the 10-day disabled list with a strained right hamstring. Frazier left Sunday's 5-2 win at Cincinnati after he grounded into a double play in the third inning. OF Jordan Luplow and RHP Dovydas Neverauskas were promoted from Triple-A Indianapolis, and RHP Johnny Barbato was sent down to Pittsburgh's top farm club.

Cubs: Lester threw 47 pitches to Willson Contreras and Kyle Schwarber during a simulated game. Lester, who is on the DL with left lat tightness and general shoulder fatigue, could need a minor league rehab start. "I think a lot of it will depend on how he feels tomorrow, how he feels like he came through today," general manager Jed Hoyer said. "I thought he looked good. It looked like the ball was coming out well." ... Contreras (right hamstring strain) also took early batting practice. ... SS Addison Russell (right foot strain) and RHP Justin Grimm (finger infection) each made their first rehab appearance with Triple-A Iowa. Russell went 1 for 3 with a double, and Grimm allowed a run while pitching one inning.

UP NEXT

Pirates right-hander Chad Kuhl and Cubs right-hander Jake Arrieta pitch in the second game of the series on Tuesday night. Kuhl (6-9, 4.52 ERA) is 3-2 with a 3.33 ERA in five August starts. Arrieta (13-8, 3.49 ERA) has been on a roll since the All-Star break, going 5-1 with a 1.78 ERA in eight outings.

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Jay Cohen can be reached at http://www.twitter.com/jcohenap

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