It's September: Do you know where your Cubs and White Sox are?

Could this really happen?

Will it happen?

What has been mostly unimaginable in the past concerning Chicago baseball remains a real possibility as the major-league season reaches September.

The Cubs and the White Sox meeting in the World Series.

"I think it's way too early to even assume anything like that," Cubs manager Lou Piniella said this weekend. "I think the White Sox have a pennant race going with Minnesota, and we still haven't won our division. I think it's way too early to assume anything."

Not since they faced each other in the 1906 World Series have the Cubs and the White Sox even made it to the postseason in the same year, but both are in first place as the calendar flips to September.

Only a collapse of monumental proportions over the final 25 games will prevent the Cubs from going to the playoffs, whether it's as NL Central champion or the National League wild-card representative. The Cubs' 85-52 record is best in the majors.

The White Sox' chances are much shakier. They lead the AL Central, but by only a half-game over the Minnesota Twins with 26 games left for the South Siders.

The schedule

Cubs: After completing a three-game series with Houston on Wednesday, the Cubs play 16 of their final 22 games away from Wrigley Field, where they are 51-21.

The Cubs still have six games remaining with second-place Milwaukee and six with St. Louis. The first three games with the Brewers will be Sept. 16-18 at Wrigley Field.

"It's a tough stretch that we have coming up, but I like our pitching staff," Cubs second Mark DeRosa said.

The Cubs would love to have a playoff spot clinched before a final week of the season that has difficulty written all over it: four games in New York against the Mets, likely to be a desperate team at that point, and the last three of the season at Miller Park.

The Brewers have 16 of 26 at home in September and begin a 10-game homestand tonight.

White Sox: It's 13 at home and 13 on the road in what promises to be one tough month.

The Sox play three games against the AL West-leading Los Angeles Angels starting Friday at U.S. Cellular Field; the Angels are 40-25 on the road.

A four-game series at Yankee Stadium starting Sept. 15 looms large as it starts a critical 10-game road trip for the Sox.

But the biggest series of the month figures to be the three-game set in Minnesota against the Twins starting Sept. 23 that kicks off the final week of the season.

Those are the only games remaining between the two rivals who have been separated by more than 1 game only twice since July 30.

"It's going to come down to that last week," Sox pitcher Mark Buehrle said.

White Sox manager Ozzie Guillen is more concerned with the present than looking ahead to that Twins series.

"It's too far ahead," Guillen said. "Hopefully we'll be 10 games up.

"It's all about the competition, the excitement (in September). It's about the players, how much they want it, how much they prepare for it. We're fine. I think everybody is mentally prepared for it."

The Sox close the season with three games at home against Cleveland, while the Twins host Kansas City. Before their series with the Sox, the Twins will have what should be a tough four games on the road against Tampa Bay (Sept. 18-21).

The concerns

Cubs: Carlos Zambrano's "arm fatigue" will no doubt be the biggest story to watch over the final month.

Zambrano's scheduled Sunday start was pushed back to Tuesday or Wednesday, but the Cubs insist everything is fine with their ace.

"He's not in any pain at all," pitching coach Larry Rothschild said. "His arm feels good."

Rookie reliever Jeff Samardzija also will bear watching down the stretch in his first pennant race. Should Samardzija struggle, Piniella could return to Bob Howry in those situations before handing the ball to Carlos Marmol and Kerry Wood.

White Sox: Concerns? Pitching, mostly.

The Sox need a healthy return of setup man Scott Linebrink, who has been sidelined since July with a sore shoulder. Linebrink is expected to come back this week, but his effectiveness will be anyone's guess.

Starter John Danks also worries the Sox, whether they want to admit it or not. Danks already has pitched 21 more innings than at any point in his career with a month still to play.

One last thing to watch with the Sox: Can they keep up their torrid home run pace as the weather turns cooler? It's a team that lives and dies with the longball.

Pedal to the mettle

Cubs: Aramis Ramirez already has driven in 100 runs and needs to keep producing into October for the Cubs to even think World Series.

White Sox: Carlos Quentin's 36 homers and 100 RBI have him on an MVP pace. Where would the Sox be without him? Certainly not in first place today.