Tampa Bay is also tied with the Angels, who split their day-night doubleheader with the Rangers.
The Rays have won 10 of their past 11 games.
"It's always about maintaining a slight mathematical chance," Rays manager Joe Maddon said. "We were in the same boat last year. ... We just have to go home and play our game. I still believe we can do this. But regardless, you have to appreciate our guys. That's 10 out of 11 at this time of year, under these circumstances where we can't have a hiccup."
Monday's key games to watch (all times ET)
Orioles (Chen, 12-10) at Rays (Cobb, 10-9), 7:10 p.m. Preview >
Rangers (Perez, 1-3) at A's (Parker, 12-8), 10:05 p.m. Preview >
Angels (Wilson, 12-10) at Mariners (Hernandez, 13-8), 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: Friday
Division Series: Oct. 6-12
AL Championship Series: Oct. 13-21
NL Championship Series: Oct. 14-22
World Series: Oct. 24-Nov. 1