Baseball's postseason races checked in early with games under the mid-September sun on a spectacular Saturday afternoon across the Majors, and the contenders kept on churning into Saturday night, juggling and jostling for position.

As the Pulse of the Postseason got hearts racing for another day, the Reds put their collective foot down as the No. 2 National League Wild Card, their NL Central rivals the Cardinals and Pirates wound up knotted up again, and the Red Sox, Braves and A's each took another step closer toward a division title.

But it was the American League Wild Card that remained so compelling, with the Rays dodging raindrops in Minnesota and catching the Rangers at the top -- but the race becoming even tighter. Saturday left that race in beautiful disarray, featuring six teams within 3 1/2 games of each other after Saturday's slate was complete.

The Royals won a 1-0 thriller over the AL Central-leading Tigers and are now tied with the Orioles at 3 1/2 out, the Yankees are three out, and the team closest to that coveted postseason spot is the Indians, at just 1 1/2 game out.

"It's fun because everything counts right now," said Indians starter Ubaldo Jimenez, the winner Saturday as Cleveland topped the White Sox. "You have to bring your A-game to the table every single day. It doesn't matter who you're facing. You have to go against them with everything you have.

"You never know what game is going to make the difference."

Another day of pulse-pounding action heading toward the postseason began Saturday afternoon in three cities where the postseason races were front and center, five of the six teams involved having postseason aspirations. Three teams would take steps forward in their quest, while three took steps back.

In Boston, the Red Sox knocked their magic number down to six, getting ahead of CC Sabathia and the Yankees and holding on for a 5-1 victory that does as much damage to their rivals as it helps their own cause. 

Jon Lester was masterful in the victory for the Red Sox, going eight innings while allowing one run on three hits, and Boston will be eyeing a sweep in its Sunday night finale against the Yanks.

In Milwaukee, the Reds were up against the Brewers, out of the race but winners of the opener of the weekend series. Cincinnati scored one more run in the first inning than it scored the night before, thanks to Shin-Soo Choo's leadoff double, and that was just the beginning for Choo on this day. He also had a two-run homer, and he added a sacrifice fly for the team's seventh run in a 7-3 win after scoring on Joey Votto's mammoth blast in the sixth.

The win stemmed the tide of the Nationals' recent rush toward the Reds, their lead in the NL Wild Card back up to 5 1/2 after the Nats lost to the Phillies.

In Texas, the concept of scoring early continued, as the A's got on the board in the first inning when Brandon Moss doubled off Yu Darvish, sending Josh Donaldson sprawling across the plate for a 1-0 lead. With Darvish and Bartolo Colon going toe-to-toe and Grant Balfour picking up the save, that was the final score -- not exactly a typical outcome for a day game at Rangers Ballpark in Arlington.

Whatever the recipe, it was another big one for the A's, winners of eight of 11 and 12 of 15. That was Darvish's fourth 1-0 loss of the season, becoming the first Major League pitcher with that dubious distinction since Orel Hershiser in 1989.

The A's are now 5 1/2 games ahead of the Rangers in the AL West, with just 14 games to play, for a magic number of 10. For reference, the Rangers led the A's by three games with 14 games to play last year, but there were six more meetings between the two teams -- not just one, Sunday's.

"This is the position you fight to put yourself in all year," said Moss. "Now we have to finish it."

The Orioles, meanwhile, did not help themselves in Toronto, falling, 4-3, to the Blue Jays, with closer Casey Janssen capping off the game with a fielding gem to nail Manny Machado, who earlier had become the youngest player in Major League history to hit 50 doubles in a season.

As night games arrived, the Royals followed the way of the A's, scoring early and then holding on for dear life. Kansas City got on the board when Eric Hosmer tripled home Alex Gordon, and the Royals closed down the Tigers for the final out on a spectuacular play to nail Prince Fielder at the plate -- Gordon to Alcides Escobar to Salvador Perez.

"They executed that play to perfection and the only thing was when I saw the throw come in, I thought Perez might get a bad hop, but he made a terrific pick on that ball and the tag," Tigers manager Jim Leyland said.

Obviously, pitching had something to do with it, too. Ervin Santana joined with three relievers for the shutout, Greg Holland finishing it with his 43rd save.

The Indians, meanwhile, took it to another AL Central club, beating the White Sox for the third time in as many days, 8-1. It was Cleveland's 11th consecutive victory over the White Sox, this time on the strength of homers from Lonnie Chisenhall and Asdrubal Cabrera, along with Jimenez's third straight win.

With the Rays' game delayed in Minnesota, so, too, was the outcome of the AL Wild Card for the night. The Rays led, 2-0, when play was halted for more than two hours, and they kept on going once the tarp was removed at Target Field, knowing full well they would tie the Rangers and keep the other teams at bay.

And so they did, building up to a 7-0 victory that solidified their status in the race. It also kept Boston's magic number at six for the division crown.

The NL Central's leaders went different directions Saturday and wound up in the same place -- tied atop the division standings, again. The Pirates tied the game on a solo homer by Jose Tabata and took the lead on one by Marlon Byrd for a 2-1 win over the Cubs. Rookie Gerrit Cole pitched seven innings of one-run ball for the win, as the Pirates raised the Jolly Roger with their 86th win.

The Cardinals fell behind the Mariners for the second straight night but didn't have a comeback in them this time, losing, 4-1, to the Interleague foes and dropping into the tie with the Pirates, both teams 2 1/2 ahead of the Reds.

At the end of the night, the Braves and Dodgers wound up with the same magic number, at four. The Braves beat the Padres, 2-1, and the Nationals snapped their seven-game winning streak with a 5-4 loss at home to the Phillies. The Dodgers stayed where it was when they lost to the Giants, 19-3, in a game San Francisco set the record for most runs scored in a single game by a team at Dodger Stadium, combined with the D-backs' 9-2 victory over the Rockies.

When the Pulse of the Postseason picks up again Sunday, the Yankees and Rangers will be trying to avert sweeps against their rivals, and they'll be doing it with a September sense of urgency.

For Yankees manager Joe Girardi, there's no denying the importance of Sunday's game at Fenway Park against the charging Red Sox, whatever label one might use about it.

"It's only a must-win game when it's an elimination game, but I think it's a real important game," Girardi said.

It will be Ivan Nova on the mound for the Yankees under the Sunday night lights in the second start back in the rotation for Red Sox ace Clay Buchholz, who has yet to lose in 2013.

All due respect to Girardi's opinion, but the Rangers' Elvis Andrus puts Sunday's finale against the A's -- and, well, the rest of the schedule -- in a different category.

"Every game right now is a must-win situation," Andrus said. "That's the way we have to face it right now and not take anything for granted. We have to keep fighting and take care of business."

All eyes will be on the Rangers and Rays again, with the Rays seeking a sweep at Minnesota to stay atop the AL Wild Card standings. The Indians seek a four-game sweep of the White Sox, while the Orioles will try for the series win in Toronto and the Royals will be playing the rubber game of their lives in Detroit with Max Scherzer going for his 20th win, again.

The Pirates will be trying to claim a home series against the Cubs, sending Cubs nemesis Francisco Liriano to the mound -- he has allowed just two earned runs on eight hits in 23 innings against the Cubs this season, good for a 0.78 ERA, including a complete-game victory on July 5.

Reds veteran Bronson Arroyo takes on the Brewers and Cards phenom Shelby Miller will meet the Mariners as the NL Central rivals finish off the weekend.

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

Orioles (Gonzalez, 9-7) at Blue Jays (Buehrle, 11-8), 1:07 p.m. Preview >

Royals (Guthrie, 14-10) at Tigers (Scherzer, 19-3), 1:08 p.m. Preview >

Cubs (Wood, 9-11) at Pirates (Liriano, 16-7), 1:35 p.m. Preview >

Phillies (Cloyd, 2-4) at Nationals (Zimmermann, 17-8), 1:35 p.m. Preview >

Padres (Smith, 0-1) at Braves (Teheran, 12-7), 1:35 p.m. Preview >

Reds (Arroyo, 13-11) at Brewers (Gallardo, 11-9), 2:10 p.m. Preview >

Indians (McAllister, 7-9) at White Sox (Sale, 11-12), 2:10 p.m. Preview >

Rays (Price, 8-8) at Twins (Hernandez, 3-1), 2:10 p.m. Preview >

Mariners (Ramirez, 5-1) at Cardinals (Miller, 13-9), 2:15 p.m. Preview >

A's (Parker, 11-6) at Rangers (Perez, 9-4), 3:05 p.m. Preview >

Rockies (Chacin, 13-8) at D-backs (Delgado, 4-6), 4:10 p.m. Preview >

Giants (Vogelsong, 3-5) at Dodgers (Volquez, 9-11), 4:10 p.m. Preview >

Yankees (Nova, 8-4) at Red Sox (Buchholz, 10-0), 8:05 p.m. Preview >

If the postseason started today ...

AMERICAN LEAGUE

Wild Card: Rays at Rangers
Division Series: Wild Card at Red Sox | Tigers at A's

NATIONAL LEAGUE

Wild Card: Reds at Cardinals/Pirates
Division Series: Wild Card at Braves | Cardinals/Pirates at Dodgers

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 »

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
AL Championship Series begins: Oct. 12
World Series begins: Oct. 23