The 25-year-old Lynn, in his first year in the Cardinals' starting rotation, is 13-4 with a 3.42 ERA in 20 starts.
Lynn is coming off a ragged performance in his last outing on Friday, when he got the win in a 9-6 victory over the Cubs despite giving up eight hits and six earned runs in five innings.
The six runs matched a season-worst for Lynn, but he wasn't too critical of his performance, choosing instead to credit the Cubs.
He had faced the Cubs in his previous start and, "It just seemed like they knew what I was trying to do," said Lynn, who had allowed only one run in his first 13 innings after the All-Star break.
"They weren't going to get beat on that today. The time before, I was able to make pitches and get out of innings with runners on. Today, when they got the runner on, they scored."
Lefty Christian Friedrich was scheduled to be the Rockies' starter on Thursday, but the club announced on Wednesday that he won't pitch until Sunday against the Giants.
"We'll back him up a couple days, then put him back out there," manager Jim Tracy said. "He's a little stiff and sore. [He has] some tightness in his lower back."
Right-hander Alex White, who was acquired in the Ubaldo Jimenez trade last July, will be recalled from Triple-A Colorado Springs to make the start.
White has made 10 starts for the Rockies this season, and is 2-6 with a 6.45 ERA, but was dominant in his last two starts with Colorado Springs.
He pitched seven scoreless innings against Tacoma on July 23, allowing four hits and striking out two, then followed that by pitching eight innings against Fresno on Saturday, allowing one run and striking out eight.
Cardinals: Furcal still day to day
The Cardinals might be without Rafael Furcal again on Thursday, as he's dealing with lower back stiffness. Furcal has not played since Friday.
Rockies: Helton, Cuddyer uncertain
The status of first baseman Todd Helton and right fielder Michael Cuddyer for Thursday's game is uncertain after they were held out of Wednesday's game. Helton was suffering from flu-like symptoms and Cuddyer has a sore right oblique.
Tyler Colvin started in place of Helton on Wednesday, and Andrew Brown started for Cuddyer.
Lynn's rough outing against the Cubs was the only start of less than six innings by a Cardinals starter since June 30.