By Bruce Levine–

CHICAGO (CBS) — With an array of Cubs rotation members having spent time on the disabled list this season, including ace Jon Lester presently, left-hander Mike Montgomery has been indispensable in his multi-purpose pitching role.

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Montgomery reminded everyone of that much Monday night, when he threw seven innings of one-run ball to lead the Cubs to a 6-1 win against the Pirates at Wrigley Field. He’s been an unlikely savior as a long man and spot starter, filling any role when the Cubs need help.

“We had a good game plan going in,” catcher Alex Avila said after Montgomery struck out four, walked none and scattered six hits. “For the most part, he executed it very well. This was overall a good game for him.”

Montgomery has had his top form of late, allowing just one earned run — a solo shot to Jody Mercer to lead off the eighth inning Monday — in his past 17 1/3 innings.

“He was really good,” manager Joe Maddon said. “You saw the ground balls (induced), much better strikes and counts. When he puts the ball on the ground, he is tough. He did a nice job of getting ahead. He really pitched primarily with his fastball. It was really impressive.”

Montgomery took over a rotation spot in the second week of June when Kyle Hendricks headed to the disabled list and held it until the second half of July. He’s stepped in for Lester in his last two starts, winning both.

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With Lester due back as early as this weekend, Montgomery’s role moving forward is unclear. The Cubs just know he’ll be ready for anything.

“We hope he just continues to pitch well,” Maddon said when asked what happens to Montgomery when Lester returns. “We have not discussed using the sixth man. That would be the primary way to do it. Some of that may be dictated by watching our guys go through their next starts. I don’t see any fatigue with our group now.”

Montgomery has become more accustomed to his changing role.

“Mentally after what I have done this season and last year, I have found what works,” Montgomery said in reference to his dual role as long reliever and starter. “I feel comfortable there. It is always a challenge to stay sharp no matter what role you are in. My focus is to keep myself physically and mentally prepared for the next month.”

Both John Lackey and Jake Arrieta are free agents in November, and the Cubs have admitted Mongomery has earned a look as a full-time starter beginning next season.

“We will consider all of his contributions when we go into next season,” general manager Jed Hoyer said. “His versatility is really valuable for us. We are going to need six or seven starters, it won’t be just five, and he will be one of them.”

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Bruce Levine covers the Cubs and White Sox for 670 The Score and Follow him on Twitter @MLBBruceLevine.