The Astros, meanwhile, will try to spoil the Brewers' late-season comeback.
"They've got some power, they've got some speed, they've got an MVP in the three spot who's dangerous," interim Houston manager Tony DeFrancesco said. "I'm just excited [the Astros] didn't quit. They got another chance to knock a team out of the playoffs. We're trying to win every game."
Saturday's key games to watch (all times ET)
Astros (Keuchel, 3-7) at Brewers (Estrada, 4-7), 7:10 p.m. Preview >
Nationals (Zimmermann, 12-8) at Cardinals (Lohse, 16-3), 7:15 p.m. Preview >
Rockies (Chatwood, 5-5) at Dodgers (Blanton, 9-13), 10:10 p.m. Preview >
If the postseason started today ...
This is how the teams would match up: Postseason Bracket »
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 the 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 the 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