CINCINNATI -- With his back facing home plate, Cubs starter Jon Lester picked up the rosin bag off the back of the mound and then fired it forcefully to the dirt. A white cloud rose and disappeared, and Lester turned his attention back to the task at hand.

That moment came after Aristides Aquino delivered a run-scoring single in the third inning of Sunday's 6-3 win over the Reds at Great American Ball Park. And that hit came shortly after Lester fumed over an inside pitch that was deemed ball four to Reds slugger Eugenio Suarez. It was a show of frustration that provided a fitting snapshot of the fire housed within the unquestioned leader of Chicago's rotation.

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And yet, Lester recently referred to himself as the "weakest link" in the Cubs' starting staff.

"That's just Jon being himself," Cubs manager Joe Maddon said. "Part of it, I think, is he actually believes that, which is not true."

Lester was not brilliant against Cincinnati on Sunday, but the 35-year-old left-hander was effective in keeping the Reds' potent lineup in check for five frames. It was the kind of outing that bought the Cubs' lineup time to wait out the stellar right arm of Luis Castillo and break through when Cincinnati decided to turn to its bullpen.

In the seventh inning, Nicholas Castellanos welcomed Michael Lorenzen to the game with a two-out single and then Kris Bryant launched a three-run home run to put the Cubs ahead for good. Ian Happ added an insurance solo shot in the eighth. That late push took Lester off the hook for a tough-luck loss and made the lefty's workmanlike performance hold up in importance due to the trip to the win column.

“I guess sometimes I have to eat my own words,” Lester said. “I kept them in the game and gave them a chance and they rewarded us. So, that was good.”

The National League Central-leading Cubs picked up bookend victories in this four-game series, splitting the set with a Reds club that is trying to force its way back into the division and Wild Card races. Cincinnati certainly has the rotation to make a late-season run, but the Cubs also feel their starting staff holds up against any other group in the NL.

Lester remains a critical part of that for the Cubs.

"I just have so much respect for him," Maddon said. "Having had the privilege of managing him for the last several years, I've seen the bad moments and then I've seen the rebounds. So I expect the rebound."

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To Maddon's point, Lester allowed eight runs in an Aug. 11 outing against the Nationals last season, and then posted a 1.71 ERA in his final eight regular-season games. Lester had a seven-run clunker late in 2017, and then gave up four earned runs in his next five appearances (three in the playoffs). He had an eight-run setback on July 3 in '16, and then went 10-1 with a 2.18 ERA down the stretch. Oh, and then the Cubs won the World Series.

Maybe Sunday's outing will mark Step 1 in Lester's latest rebound.

Over his five innings, Lester piled up seven strikeouts and scattered five hits, including an opposite-field solo homer to Suarez in the fifth. The lefty also allowed two runs in the third, when Joey Votto delivered an RBI double and Aquino had his RBI single. Between those setbacks was the walk to Suarez, though Lester barked at home-plate umpire Angel Hernandez following that free pass.

“I showed my emotion a little bit -- probably shouldn't have,” Lester said. “But it's frustrating sometimes when you do locate and you don't get the call.”

Last time out, Lester surrendered 11 runs (nine earned) in a four-inning, 94-pitch disaster on Tuesday, when the Cubs' bullpen was short-handed. Heading into Sunday, the lefty had given up 16 runs (14 earned) combined in his past two starts (nine innings). Maddon looked at the peripheral numbers and came away with the sense that -- outside of some usage and command issues -- Lester was fine.

As an example, Lester averaged 88.3 mph on his cutter on Sunday -- up from his season average of 87.8 mph, per Statcast. The lefty's average fastball was 90.6 mph, which is exactly his average for the 2019 season as a whole. All his other offerings followed a similar pattern. There has been nothing on the surface to raise any red flags.

“He threw the ball really well. He was good. He was very good,” Maddon said. “They hit the home run, but otherwise, the ball was well placed against him. I thought the numbers were good on the board again. I thought the location was better and [he had] a more pertinent curveball.”

When asked about Lester’s “weakest link” assessment, Bryant smirked.

“He just has high expectations of himself -- just like any of us here,” Bryant said. “He's the last guy that is the weakest link. The guy's in his 14th season. He's been doing it for so long. Completely underrated left-hander. But, it just goes to show you how tough he is on himself.”