MILWAUKEE -- Kris Bryant stopped by the office of Cubs manager Joe Maddon following Saturday's loss to the Brewers. The third baseman has been trying to stay on the field as he works through a right knee issue, but the discomfort flared up again in his latest attempt.

"When he comes in and says he needs a day, then you know," Maddon said prior to Sunday's series finale at Miller Park. "Because, he's played through a lot of different maladies."

Bryant was out of the starting lineup for Sunday's game against the Brewers and the All-Star third baseman will remain in day-to-day mode when the Cubs head to San Diego next. The setback came one day after Chicago learned that star shortstop Javier Báez is likely to miss the rest of the regular season with a hairline fracture in his left thumb.

That is not where the Cubs' question marks end, either.

Anthony Rizzo recently returned from another bout with a back issue. Willson Contreras is still easing back into things following a month-long comeback from a hamstring injury. Ben Zobrist rejoined Chicago on Sept. 1 following a four-month hiatus on the restricted list. Craig Kimbrel is on the injured list. Yu Darvish just came back from a forearm setback.

Maddon said last month that "September creates its own energy," and was asked Sunday if he still felt that way.

"It needs to right now. It needs to," Maddon said with a chuckle. "Please, Mr. September, bring it on. We're ready for your energy. Normally this time of the year, we've parceled out the year to the point that we are not beat up, not tired, not hurt. ... This year, it's been harder to do that."

The knee problem dates back to late June for Bryant, who first left a game with the issue back on July 24 in San Francisco. In the 37 games dating back to July 26, when he returned to the field, Bryant has hit .226/.307/.372, watching his season OPS drop to .889 from .967 in the process. He has posted a 29.4 percent strikeout rate in that span (compared to 20.1 percent before July 26).

More recently, Bryant was out of the lineup on Tuesday against the Mariners due to the knee issue but rejoined the lineup on Thursday following the team’s day off on Wednesday. He went 2-for-9 in the first three games of the series against the Brewers, lowering his slash line to .200/.321/.267 with no home runs and one RBI in his last 14 games.

Bryant said on Thursday that he did not believe the knee was tied to his hitting woes.

"There's always nicks and bruises and stuff you've just got to deal with," Bryant said. "Obviously, an offseason will make it feel much better, when you have an extended amount of time off. But we don't have that. We have games we've got to win."

While Bryant would not use the knee as an excuse for his diminished production, Maddon said there is no denying that it has likely played a role.

"It's bothering him in all aspects of the game," said the manager. "I think any athlete you speak to is going to say the same thing. That's just being a Major League baseball player. It's immeasurable, I think, when it really comes down to it, how much it is or isn't [affecting him]. You just don't know that. But you know the guy's not feeling well."

Maddon noted that there was a foul ball late in Saturday's game after which Bryant struggled to quickly regain his balance. In fact, Bryant fouled an inside pitch from Brewers closer Josh Hader off his right leg (near the knee) in the eighth inning of Chicago's 3-2 loss.

Maddon said there have been other swings he has noticed of late that have not looked right when compared to Bryant's typical mechanics.

"He catches himself on his finish sometimes, trying to find his balance," Maddon said. "There's definitely something that’s causing kind of a weakness there, it looks like."

For the Cubs, it is yet another obstacle in a season that has been filled with them, hindering Chicago's push for a fifth straight postseason berth. The North Siders are still in the thick of the October chase, and Maddon continues to insist that it needs to be the lineup -- even with the mounting troubles -- that powers a late-season run.

"It's still there," Maddon said. "Again, Willson's back. Zobrist is there. We've got Rizzo. You've got [Kyle] Schwarber swinging the bat really well. [Nicholas] Castellanos. There's still a lot of offense out there. We just have to be able to, on a nightly basis, bring it to the forefront."