Jon Lester exits with stiff back, Cubs’ lead down to one after loss to Brewers

And you thought Packers quarterback Aaron Rodgers was going to be as bad as it got for Chicago fans this week.

Less than 24 hours after the Bears’ collapse in Green Bay, the baseball season got very real very quickly for the Cubs, who have led the National League Central and have had the best record in the league the entire second half.

Five-plus innings into the opener of a critical series against the second-place Brewers, the Cubs watched 15-game winner and ace Jon Lester leave the game because of tightness in his lower back. They went on to lose 3-2 to see their division lead shrink to one game.

That’s the smallest the Cubs’ lead has been since Aug. 5. The Brewers have made up 3½ games since Thursday, with the last two games of the season series coming up the next two days.

‘‘They’re good,’’ manager Joe Maddon said of the Brewers, who have won 10 of their last 12 games. ‘‘When Liston fought Ali, it wasn’t just a walk in the park for Ali.

‘‘We have to play at the top of our game to beat them. . . . It’s not easy putting the Brewers away.’’

It might be harder for the Cubs to put anybody away if Lester’s back continues to bother him into Tuesday and if slugger Kyle Schwarber’s back pain lingers much longer.

Maddon said he considers Lester’s back to be a minor issue after he seemed to improve quickly after leaving the game.

‘‘I think it’ll be fine — hopefully,’’ said Lester, who allowed back-to-back two-out hits in the sixth before leaving. ‘‘It’s not anything painful, just kind of uncomfortable. After I got out of the game and came up here, it felt a lot better. Hopefully tomorrow will be the same.’’

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Lester said he’s not sure whether he hurt it on a swing-and-miss in the fifth.

‘‘I came back in, sat down and was fine,’’ he said. ‘‘And then I went to stand up to go out there, and it didn’t feel all that great. I don’t know if that was it or just [pitching one inning before a rainout] Friday to today or what. But I don’t think it’s going to be anything that’s going to stick around.’’

With the score tied 2-2, Lester struck out Jonathan Schoop for the second out of the sixth. But third baseman Javy Baez and catcher Willson Contreras immediately signaled to the dugout and approached the mound. After a brief visit from the trainer, Lester stayed in the game.

Mike Moustakas then singled to right-center before Erik Kratz followed with a double into the right-field corner. That brought Maddon and the trainer back to the mound to retrieve Lester.

In came reliever Carl Edwards Jr., who promptly uncorked a wild pitch to allow what proved to be the winning run to score.

Lester’s next start would be Saturday. And if weather forces another postponement of the makeup game Thursday against the Nationals in Washington, the Cubs wouldn’t need a fifth starter until Sept. 19 should Lester be sidelined or need extra time.

Meanwhile, a team in the 21st day of a scheduled 23-games-in-23-days grind now faces potentially its toughest stretch drive of this four-year competitive window.

The Brewers are hot. The Cubs have lost three games in a row and five of their last seven. The bullpen is teetering. A rotation that already has plugged in its sixth starter (Mike Montgomery) and traded for another (Cole Hamels) now monitors the health of its ace. And the lineup is an abyss after the first five in the order, especially with Schwarber out for at least a few more days.

‘‘I’m really pleased with how our guys have fought through all this,’’ Maddon said.

With maybe their biggest fight of the season facing them in the final 19 games.