Just when it seemed the Wild Card races couldn't get any wilder, Thursday's games offered a bit of clarity in both leagues, as the teams at the top put a bit of separation between themselves and their closest pursuers.

Thursday's action began with the Orioles sweeping the Rays with a dramatic 3-2 victory in 14 innings. Manny Machado's walk-off single -- just out of the reach of a sprawling Matt Joyce, whose Rays now sit four games back -- gave the Orioles a fleeting half-game lead over the Yankees for first place in the AL East, and secured their first season at .500 or better since 1997.

Wells Fargo

"There's a bigger goal in mind, and that wasn't the goal from Day 1 this spring," Orioles manager Buck Showalter said. "It's like watching other teams for years and saying, 'We want to do what they're doing. We'd like to get a chair at the dance.'"

Later in the afternoon in Anaheim, Jered Weaver pitched a gem after missing his last start because of right biceps tendinitis. The Angels' 6-0 victory moved them to 3 1/2 games out of the Wild Card and 4 1/2 behind Oakland, which currently holds the top Wild Card slot.

"Every game's important, man," Weaver said. "We're trying to go out there and win every game and see what happens."

The night games saw the National League take center stage, after the Yankees had wrapped up their 2-0 victory over the rival Red Sox. Phil Hughes tossed 7 1/3 shutout frames, as New York kept pace with Baltimore atop the AL East.

The red-hot Phillies had a four-run lead slip away in Houston and, as a result, their seven-game winning streak was snapped and their Wild Card deficit stretched to four games.

That's because in the lone late game, the Cardinals held on for a crucial 2-1 victory over Los Angeles. St. Louis -- now two games up on Los Angeles -- cemented itself as the team to catch for the National League's final playoff spot.

In Chicago, the Tigers-White Sox clash was washed away by rain and rescheduled for Monday. The South Siders hold a one-game edge heading into the weekend.

Friday's key games to watch (all times ET)

Pirates (McDonald, 12-7) at Cubs (Rusin, 0-2), 2:20 p.m. Preview >
The slumping Pirates are still in the thick of the Wild Card race despite having lost six straight. James McDonald looks to end that skid.

Tigers (Verlander, 13-8) at Indians (Kluber, 1-3) 7:05 p.m. Preview >
One game back of the first-place White Sox, the Tigers look to pull even in the AL Central when they head to Cleveland for the first of a three-game set.

Rays (Price, 17-5) at Yankees (Sabathia, 13-5), 7:05 p.m. Preview >
A couple of aces take the hill in the Bronx as the Rays, trailing the Yankees (and Orioles) by four games, face a crucial series in terms of staying alive.

Reds (Arroyo, 12-7) at Marlins (Turner, 1-3), 7:10 p.m. Preview >
Sitting comfortably atop the NL Central, the Reds' magic number sits at eight when Bronson Arroyo takes the ball in Game 1 in Miami.

Nationals (Detwiler, 9-6) at Braves (Medlen, 8-1), 7:35 p.m. Preview >
The Nationals have the NL East all but locked up, and the Braves -- Washington's closest challengers -- are looking to take a similar stranglehold on the top Wild Card spot.

Phillies (Hamels, 14-6) at Astros (E. Gonzalez, 2-0), 8:05 p.m. Preview >
Hoping to start another winning streak, the Phillies look to rebound from a tough loss to Houston on Thursday by sending lefty Cole Hamels to the hill.

Mariners (Iwakuma, 6-4) at Rangers (Darvish, 14-9), 8:05 p.m. Preview >
The Rangers are hoping to preserve their three-game lead over Oakland in the AL West, as Yu Darvish takes the mound in the first of three against Seattle.

Angels (Wilson, 12-9) at Royals (Chen, 10-12), 8:10 p.m. Preview >
The Angels are hoping a three-game set in Kansas City signals the start of a late playoff push. They trail by 3 1/2 games for the second Wild Card in the AL.

White Sox (Sale, 16-6) at Twins (Vasquez, 0-1), 8:10 p.m. Preview >
Coming off a rainout against Detroit on Thursday, the White Sox send their ace, Chris Sale, to the hill against Minnesota, looking to preserve their one-game lead over the Tigers.

Mets (Niese, 10-9) at Brewers (Friers, 9-7), 8:10 p.m. Preview >
The best-kept secret in the NL Wild Card hunt, Milwaukee sits just 3 1/2 games out of a playoff spot as it starts a series against the Mets.

Giants (Cain, 13-5) at D-backs (Skaggs, 1-1), 9:40 p.m. Preview >
The Giants are simply trying to put separation between themselves and the rest of the NL West, while the D-backs sit 4 1/2 games out of the NL Wild Card.

Orioles (Saunders, 8-11) at A's (Milone, 12-10), 10:05 p.m. Preview >
Two of baseball's biggest surprises this season square off in Oakland, with each hoping to put a tighter grip on the playoff spots they find themselves currently holding.

Cardinals (Kelly, 5-6) at Dodgers (Capuano, 11-10), 10:10 p.m. Preview >
With the Cards' lead in the NL Wild Card race at two games, the slumping Dodgers look to make a statement Friday in the second of four at Chavez Ravine.

If the postseason started today ...

AMERICAN LEAGUE
Wild Card: Orioles or Yankees at A's
Division Series: Orioles or Yankees vs. White Sox | Rangers vs. Wild Card winner

NATIONAL LEAGUE
Wild Card: Cardinals at Braves
Division Series: Reds vs. Giants | Nationals vs. Wild Card winner

Postseason Bracket »

Postseason 101

Magic numbers
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.

Tiebreaker scenarios
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 »

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