When the White Sox traveled to Detroit to open a series with the Tigers on Aug. 31, they held a three-game American League Central lead. One sweep later, the division was tied, but the Tigers since have lost six of seven. That includes Monday's series opener at U.S. Cellular Field, where sixth-inning back-to-back homers by Alex Rios and A.J. Pierzynski keyed a 6-1 Chicago victory, restoring the White Sox's three-game division advantage.
"Listen, they're a great team, but we've been playing well all year to be in this spot," White Sox second baseman Gordon Beckham said of the Tigers. "We want it. We want it bad. I know they want it. We're just going to fight it out until the end."
The Angels rudely interrupted the A's nine-game winning streak last week with a three-game sweep in Oakland. The A's exacted some measure of revenge on Monday in Anaheim, snapping the Angels' six-game win streak with a 3-1 victory behind rookie Jarrod Parker's seven stellar innings. Oakland tightened its grip on the AL's top Wild Card spot, with the Angels 1 1/2 games out of the second position.
In the night's most dramatic contest, Ryan Ludwick's 14th-inning infield RBI single sent the Reds to a 4-3 walk-off victory over the Pirates, who missed an opportunity to gain ground in the NL Wild Card race. Two other teams did just that, with the Phillies and Brewers continuing to make late runs at the Cardinals, whose hold on the second Wild Card spot slipped to one game with Monday's loss to the Padres.
In other NL action, the Nationals increased their NL East lead over the Braves to 6 1/2 games, with Gio Gonzalez becoming the Major Leagues' first 19-game winner in a victory over the Mets.
Tuesday will feature the beginning of several series featuring playoff contenders, none more crucial than the Rays' three-game set with the Orioles, who lead Tampa Bay by one game for the second AL Wild Card berth.
Today's key games to watch (all times ET)
Marlins (Eovaldi, 4-11) at Phillies (Halladay, 9-7), 7:05 p.m. Preview >
If Roy Halladay gets to double-digit wins for an eighth consecutive season, it will help the Phillies cut into the Cardinals' five-game lead for the second NL Wild Card spot.
Rays (Moore, 10-9) at Orioles (Hammel, 8-6), 7:05 p.m. Preview >
The Orioles not only hold a one-game lead over the Rays for the second AL Wild Card berth, but also for second place in the AL East, with Baltimore one behind the Yankees.
Yankees (Kuroda, 13-10) at Red Sox (Lester, 9-11), 7:10 p.m. Preview>
Hiroki Kuroda will try to help right the ship for New York, whose 10-game division lead on July 18 has shrunk to one as it starts a three-game set with the rival Red Sox .
Pirates (Correia, 10-8) at Reds (Leake, 7-9), 7:10 p.m. Preview >
The Pirates have lost four consecutive games and eight of their last 10, including a 14-inning walk-off defeat in Monday's series opener against the NL Central-leading Reds.
Nationals (Zimmermann, 10-8) at Mets (Dickey, 18-4), 7:10 p.m. Preview >
The Nationals will aim to extend their 6 1/2-game NL East lead over the Braves, but they have to get past R.A. Dickey, who can become the Major Leagues' second 19-game winner.
Indians (Jimenez, 9-15) at Rangers (Harrison, 15-9), 8:05 p.m. Preview>
Matt Harrison, 0-2 with a 9.00 ERA in his past two starts, will be tasked with fortifying the Rangers' three-game lead over the A's in the AL West.
Braves (Hudson, 14-5) at Brewers (Estrada, 2-6), 8:10 p.m. Preview >
The Brewers have gone on a 16-5 run to creep back into the NL Wild Card race, with their win in Monday's series opener putting them five games behind the Cardinals for the second spot.
Tigers (Fister, 8-8) at White Sox (Peavy, 10-10), 8:10 p.m. Preview >
The Tigers haven't trailed by as many as four games in the division since July 7, but that's what they face unless they can avoid their fifth straight loss in this one.
Giants (Bumgarner, 14-10) at Rockies (Chacin, 2-5), 8:40 p.m. Preview >
Madison Bumgarner has allowed at least four earned runs in three straight starts, but he takes the mound at Coors Field with his team holding a five-game lead in the NL West.
Dodgers (Kershaw, 12-8) at D-backs (Kennedy, 12-11), 9:40 p.m. Preview >
Clayton Kershaw was scratched from his start against the Giants on Sunday due to a sore hip, but he can help the Dodgers cut into the Cardinals' one-game lead for the second NL Wild Card spot.
A's (Straily, 1-0) at Angels (Williams, 6-7), 10:05 p.m. Preview >
The A's look to build on Monday's series-opening win, which put them two games ahead of the Orioles for the top AL Wild Card spot and 3 1/2 in front of the Angels.
Cardinals (Wainwright, 13-12) at Padres (Volquez, 9-10), 10:05 p.m. Preview >
The Cardinals, whose hold on the NL's second Wild Card berth slipped to one game on Monday, need more from Adam Wainwright, who has been hit hard in his past two outings.
If the postseason started today ...
Wild Card: Orioles at A's
Division Series: Yankees vs. White Sox | Rangers vs. Wild Card winner
Wild Card: Cardinals at Braves
Division Series: Reds vs. Giants | Nationals vs. Wild Card winner
To calculate a team's magic number, take the number of games it has remaining and add one. Then subtract the difference in the number of losses between that team and its closest pursuer.
A tiebreaker games will be played to determine a division winner, even if the tied clubs are assured of participating in the postseason. If a division championship tiebreaker is necessary, the head-to-head record between the clubs will determine home-field advantage. If the head-to-head record is tied, then division record will be the next tiebreaker.
If two clubs are tied for the two Wild Card berths, home-field advantage will be determined by the head-to-head record between the clubs. If the head-to-head record is tied, then division record will be the next tiebreaker.
2012 postseason schedule
Wild Card playoff games: Oct. 5
Division Series: Oct. 6-12
AL Championship Series: Oct. 13-21
NL Championship Series: Oct. 14-22
World Series: Oct. 24-Nov. 1
Andrew Simon is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.