Lester allowed two hits over seven innings with a season-high nine strikeouts, Willson Contreras hit a run-scoring single in the sixth inning and the Cubs beat the Cincinnati Reds 1-0 on Saturday to maintain their NL Central lead.
Justin Wilson pitched the eighth. Jesse Chavez got the first out in the ninth and Randy Rosario retired Joey Votto on a fly to warning track in left-center. Steve Cishek retired Eugenio Suarez on a broken-bat grounder to third for his fourth save, completing a four-hitter.
"We know we're going to be matched up throughout the game, and that's what Joe likes to do," Cishek said. "Everyone knows it's the ninth inning. We just try to treat it like any other inning."
Seeking their third straight division title, opened a 2 1/2-game NL Central lead over second-place Milwaukee. Chicago has won three straight, four of five and eight straight against Cincinnati.
Lester (16-6) came out after three runs and 5 2/3 innings against the Brewers on Monday because of back tightness.
"It's doing fine," Lester said. "Like I say, good drugs and good docs. We're all good."
After a midseason slump, the 34-year-old left-hander is 4-1 with a 1.73 ERA in his last six starts.
"Jonny typically gets better when he smells it," manager Joe Maddon said. "He made some really big pitches when he had to."
Chicago announced Friday that Strop has a hamstring strain, causing him to miss the rest of the regular season.
"We needed a quality start and he went beyond that," Cishek said of Lester. "Especially for us in the bullpen where we could use a little bit of rest. It was huge for us, a huge boost."
Cody Reed allowed two hits and struck out a career-high 10 in five innings, matching his longest outing this season.
"Did what he wanted him to do," manager Jim Riggleman said. "Get us to that point of the ballgame and give us a chance."
Reed threw 91 pitches after transitioning from the bullpen. He threw 91 pitches.
"It was fun out there," Reed said. "I could have kept going."
Each team had just two soft singles through five innings on an afternoon of bright sunlight and shadows that covered home plate. The lights in the 104-year-old ballpark were on when the game started shortly after 3 p.m. CDT.
"Both clubs' hitters were having a little trouble hitting, seeing with the background today," Riggleman said.
Cubs slugger Kris Bryant struck out swinging four times.
Cubs RHP Brandon Morrow, who had 22 saves in 24 chances before going on the disabled list on July 18, hopes to be activated in the next few days after throwing a 19-pitch simulated game on Saturday.
"It all depends on how I come in tomorrow," Morrow said. "I expect to feel good enough. It was a successful day."
Morrow revealed his injury was a bone bruise in his right forearm, caused by muscle overuse and a stress reaction from pitching. "Throwing too hard," he quipped.
Morrow's return figures to be a big boost for the Cubs' bullpen after Strop strained his left hamstring on Thursday in Washington running to first base.
Maddon said he doesn't think he'll initially use the right-hander in a save situation. Maddon will monitor Morrow's pitch counts and doubts the reliever will be able to throw in consecutive games unless the Cubs advance deep into the postseason.
Reds: RHP Michael Lorenzen will start in place of RHP Tyler Mahle (right shoulder fatigue) on Tuesday. Mahle's status for the remainder of the season is uncertain, manager Jim Riggleman said. The 26-year old Lorenzen hasn't make a start since September 2015, at the close of his first season with the Reds and in the majors.
Cubs: Maddon said OF/IF Kyle Schwarber (back) could be cleared for pinch hitting this weekend and return to the lineup when the Cubs travel to Arizona for a three-game series starting Monday. ... Maddon also expects OF Jason Heyward (right hamstring tightness) to return during the series against the Diamondbacks.
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