The Indians -- who began the day 1 1/2 games behind Tampa Bay and 1 1/2 games ahead of the Yankees -- were going for a four-game sweep against the White Sox on Sunday. And the Rays, tied with Texas at the top of the Wild Card hunt, are going for their own series sweep against the Twins.
The Tigers lent some clarity to the American League playoff picture with a victory over Kansas City. Max Scherzer took a no-decision on Sunday in his fifth attempt at earning his 20th victory, but he struck out 12 batters and Alex Avila homered twice to lead Detroit to a 3-2 victory.
The Royals -- right in the thick of the Wild Card hunt themselves -- dropped to four games behind Texas and Tampa Bay, and they're one game behind the Yankees and Orioles in the chase.
The action was just as compelling in the National League. The Pirates got a clutch single from veteran Justin Morneau to lift them to a 3-2 win over the Cubs and a half-game lead over the Cardinals in the National League Central. St. Louis, not to be outdone, took a commanding lead over Seattle into the late innings.
The Pirates and Cardinals can both fall back to a Wild Card position if they don't pull out the division title, but Washington continues to make that race interesting. The Nationals got 18 hits in an 11-2 victory over Philadelphia on Sunday, but the teams ahead of them in the race all held serve.
The Braves, jockeying for the best record in the NL, fell short in a 4-0 loss to the Padres on Sunday. Despite the loss, Atlanta maintains a 10-game cushion in the East and can clinch a postseason berth early this week. Washington, 10 games back in the division, has gone 9-2 in its last 11 games.
Sunday night's key game to watch (all times ET)
Yankees (Nova, 8-4) at Red Sox (Buchholz, 10-0), 8:05 p.m. Preview >
If the postseason started today ...
Wild Card: Rays at Rangers
Division Series: Wild Card at Red Sox | Tigers at A's
Wild Card: Reds at Cardinals/Pirates
Division Series: Wild Card at Braves | Cardinals/Pirates at Dodgers
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 game 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.
• Tiebreaker rules »
2013 postseason schedule
NL Wild Card Game: Oct. 1
AL Wild Card Game: Oct. 2
NL Division Series begin: Oct. 3
AL Division Series begin: Oct. 4
NL Championship Series begins: Oct. 11