Heading into the final day of the season, however, that's just about all we know.
There is still plenty to be decided in terms of division races and seeding in this year's postseason, which will begin Friday with a pair of Wild Card games.
One of those games on Friday is set: The Cardinals will head to Atlanta to face the Braves -- a year after St. Louis' epic Wild Card comeback in which it passed Atlanta on the final day of the season.
The Yankees hold the upper hand in both the American League East race and the race for the top spot in the AL following their thrilling 12-inning, 4-3 victory over the archrival Red Sox.
Raul Ibanez hit a pinch-hit, game-tying home run in the bottom of the ninth and then won it in the 12th with a walk-off single to assure the Yankees that a win on Wednesday secures both a division crown and home-field advantage in the first two rounds.
"I think it's extremely important, because you want to be able to do that," Yankees manager Joe Girardi said. "If you win, you win the division -- that's the bottom line. We have a chance to have the best record, and that's the bottom line. That's a good feeling that you can control that."
If the Yankees stumble, the Orioles are waiting to capitalize. Their 1-0 victory over the Rays kept them a game back of New York, and they could force a one-game tiebreaker in Baltimore on Thursday with a win and a Yankees loss.
Otherwise, the O's are destined for Friday's Wild Card Game. Their potential opponent? Still to be determined.
That's because the A's -- who once trailed Texas by 13 games in the AL West -- have stormed back to tie the Rangers for the division lead with one game to play. Oakland's 3-1 win over Texas on Tuesday assured that Wednesday's game will settle the AL West race.
As for tiebreakers regarding home-field advantage in either a Wild Card Game or for the top seed -- get out your notebooks:
Yankees-Rangers tie: Yankees win due to 4-3 head-to-head record.
Orioles-Rangers tie: Rangers win due to 5-2 head-to-head record.
Orioles-A's tie: A's win due to 5-4 head-to-head record.
Yankees-A's tie: A's win due to second tiebreaker, which is intradivision records. Head-to-head record was 5-5.
If the Yankees and Orioles tie for the AL East, the tiebreaker -- even though it's considered a regular season game -- would not count as far as determining home-field advantage in the postseason.
The race for the top spot in the National League is much simpler. Washington, which knocked off Philadelphia, 4-2, owns the tiebreaker over Cincinnati. That means the Nats need a win or a Cincinnati loss in St. Louis to secure the No. 1 seed.
The Reds need to win and get help from Philly to take home-field advantage throughout the playoffs.
Wednesday's key games to watch (all times ET)
Phillies (Lee, 6-8) at Nationals (Jackson, 9-11), 1:05 p.m. Preview >
The Nationals control their own destiny in the hunt for home-field advantage throughout the postseason. They'll need a win or a Cincinnati loss to secure the NL's top spot.
Rangers (Dempster, 12-8) at A's (Griffin, 7-1), 3:35 p.m. Preview >
The equations here are simple: Wednesday's winner is the AL West champion. The loser heads to a winner-take-all Wild Card game on Friday against either the Orioles or Yankees.
Red Sox (Matsuzaka, 1-6) at Yankees (Kuroda, 15-11), 7:05 p.m. Preview >
After a dramatic win on Tuesday, the Yankees' magic number sits at one. They send Hiroki Kuroda to the hill needing a win or a Baltimore loss to clinch the AL East.
Orioles (Tillman, 9-2) at Rays (Hellickson, 9-11), 7:10 p.m. Preview >
The Orioles need a win and a Yankees loss to force a one-game tiebreaker against New York on Thursday, which would take place in Baltimore. Red-hot right-hander Chris Tillman gets the ball vs. Tampa Bay.
Reds (Bailey, 13-10) at Cardinals (Miller, 1-0), 8:15 p.m. Preview >
By first pitch, the Reds will know if they have a shot at home-field advantage throughout the playoffs. They'll need a Nats loss against the Phillies and a victory Wednesday.
If the postseason started today ...
Wild Card: Orioles at Rangers or A's
Division Series: Rangers or A's vs. Tigers | Yankees vs. Wild Card winner
Wild Card: Cardinals at Braves
Division Series: Giants vs. Reds | Nationals vs. Wild Card winner
For the 2012 postseason, the team with the better record will play the first two games on the road to start the Division Series.
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.
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