Thursday would be Montgomery's fifth start for the Cubs; he has a no-decision and a 3.93 ERA, giving up eight earned runs over 18 1/3 innings. In his last start, on Sept. 7 against the Brewers, he gave up one earned run on two hits over five innings, striking out six.
The Cubs decided to flip Montgomery and Jon Lester so that Lester will close the series against the Cardinals on Wednesday. General manager Jed Hoyer said on Monday that the move had nothing to do with lining up the pitchers for the postseason.
"It's just trying to get guys the right rest, right matchups," Hoyer said.
• Hoyer has never been part of a team that secured a playoff spot early, which the Cubs could do this week.
"There's challenges that go with it," he said. "You want to make sure you're sharp going in, but you also want to make sure you're fresh. There's a double-edged sword to fight to the last day. It keeps you fresh and keeps you hungry. But there's an element where it kind of wears you down.
"If we have a chance to keep guys fresh and ready to be really good in October, I think we have to do that."
• Shortstop Addison Russell, 22, hit his 20th home run on Sunday, and is the second-youngest Cubs player to hit 20 in a season. Hall of Famer Ron Santo hit his 20th at 21 in 1961. Russell also joins Hall of Famer Ernie Banks (29 homers in 1961), Roy Smalley Sr. (21 in 1950) and Alex Gonzalez (20 in 2003) as the only Cubs shortstops to hit 20 in a season.
• Reliever Pedro Strop, on the disabled list since Aug. 11 with a torn meniscus in his left knee, is rehabbing in Chicago, and so far has had no setbacks.
Carrie Muskat has covered the Cubs since 1987, and for MLB.com since 2001. She writes a blog, Muskat Ramblings. You can follow her on Twitter @CarrieMuskat and listen to her podcast. This story was not subject to the approval of Major League Baseball or its clubs.