CHICAGO -- The Chicago Cubs fourth straight postseason appearance has been guaranteed. Whether they finish as the National League Central Division champions, however, remains up in the air.

The Cubs head into Sunday's regular-season finale tied for the first place in the division with the Milwaukee Brewers, who erased a one-game deficit in the standings with a 6-5 victory over the Detroit Tigers on Saturday.

Meanwhile, the Cubs -- who had owned the top spot in the Central since mid-July -- came up short in a 2-1 loss to the St. Louis Cardinals on Saturday afternoon at Wrigley Field, where they will wrap up their three-game series on Sunday.

Chicago's postseason future could sharpen into focus out Sunday or could be extended to Monday if Chicago and Milwaukee are still deadlocked atop the division after Sunday's games.

The Cubs would capture the division with a win and a Brewers loss.

If the Cubs and Brewers play Monday at Wrigley Field in a tiebreaker for the Central crown, the loser would host the wild card game Tuesday.

"I'd just like to continue to have the best record in the National League after (Sunday), "Cubs manager Joe Maddon told reporters Saturday, according to the team's official website. "There's nothing to lament with our guys. They've been playing hard for a long period of time. Our route has been a little different than anybody else. We'll come back ready to play (on Sunday) and see how it all falls."

Mike Montgomery will make his career-high 19th start of the season. Montgomery (5-6, 3.99 ERA) joined the starting rotation after Yu Darvish was sidelined with elbow issues earlier this year. Montgomery is 1-2 with a 2.70 ERA in 11 career outings (two starts) against the Cardinals.

Even with so much on the line, however, the Cubs won't try to control more than they can.

"It's one day at a time," Cubs outfielder Ben Zobrist told reporters. "We just think about (Sunday) and try to win (Sunday) and hope that's enough going into this coming week. Regardless, we're thinking about all of these games like they're playoff games. We stay in the moment and believe that it's going to work out for us."

Despite Saturday's win that snapped a four-game losing streak, the Cardinals saw their postseason chances vanish. The Los Angeles Dodgers win over the San Francisco Giants eliminated St. Louis from the wild card picture, which meant the Cardinals have failed to play beyond the regular season for the third straight year for the first time since 1997-99.

The Cardinals left Wrigley Field hopeful after they got a gem from starter Miles Mikolas, who shut the Cubs down over eight innings. But the Dodgers pulled out the victory they needed to join the playoff picture, locking out the Cardinals.

Rookie Jack Flaherty (8-8, 3.16 ERA) had been scheduled to start for St. Louis on Sunday, but that could change, according to the Cardinals' official website. Flaherty is 1-0 with a 0.82 ERA in three career appearances (two starts) against the Cubs.

Comment about central title is the plan as cubs host cardinals