With just six days remaining in the regular season, the races for the American League West and the AL's second Wild Card are coming right down to the wire, with the Rangers, Astros, Angels and Twins all in the mix.
Here's a look at some key developments from Monday's action that helped shape the postseason picture:
Wild West, Wild Card
The Rangers have an inside track on a postseason berth as the current leaders in the AL West, but the Astros and Angels are hot on their heels.
The Astros and Angels both won Monday to gain a game on the Rangers, who lost to the Tigers. The Rangers now lead the second-place Astros by 1 1/2 games and hold a two-game lead over the third-place Angels.
Monday's victory over the Mariners helped the Astros maintain a half-game lead for the second AL Wild Card over the Angels, who walked-off against the A's.
But don't count out the Twins, who beat the Indians to remain 1 1/2 games behind the Astros for the final playoff spot in the AL.
"It feels good but we're obviously not finished yet," said Twins third baseman Trevor Plouffe. "We've been battling all season. We've put ourselves in a good position and we're looking forward to these last six games. It's going to be a lot of fun."
The Astros have five games remaining, while the Rangers, Angels and Twins each have six games left. Of those four clubs, the only head-to-head matchup scheduled this week is a four-game series between the Angels and Rangers, which begins on Thursday in Texas.
Blue Jays in position for No. 1 seed
The Blue Jays moved one game ahead of the Royals for the AL's best record and lowered their magic number to clinch the AL East to two games over the Yankees with a comeback win over the Orioles.
The Jays can clinch their first division crown in 22 years on Tuesday, if they beat the O's and the Yankees lose to the Red Sox.
Toronto, which has a five-game lead in the division over the second-place Yankees, is guaranteed home-field advantage in the AL Division Series if it wins the AL East. Home-field advantage in the AL Championship Series is still up for grabs, with the Jays needing to hold off the Royals for the better record.
The Yankees, meanwhile, hold a 3 1/2-game lead over the Astros for the top AL Wild Card spot. The Yankees can clinch a postseason berth as early as Tuesday, provided they beat the Red Sox, the Twins lose and either the Angels or Rangers lose.
Cardinals on verge of division title
The Cardinals rallied for three runs in the ninth inning to beat the Pirates, 3-0, giving St. Louis a chance to clinch the National League Central on Tuesday with a win at PNC Park.
The Cards, who have already clinched a postseason berth, widened their division lead over the second-place Pirates to four games, with five games remaining for each club. Michael Wacha starts Tuesday for the Cardinals, who are going for a third straight NL Central title.
Should they win the division, the Cardinals would have home-field advantage in the NL Division Series and NL Championship Series, by virtue of clinching a better record than the NL East champion Mets and current NL West-leading Dodgers; St. Louis has also clinched home field in the NL Wild Card Game presented by Budweiser, should they not win the division.
While the Pirates' chances to win the division took a hit, they too have already clinched a playoff spot and lead the Cubs by 3 1/2 games for the top NL Wild Card. The Pirates' magic number to host the NL Wild Card Game remains three games over the Cubs, who enjoyed a walk-off win over the Royals on Monday.
Other things to know
• The Dodgers can clinch the NL West if they beat the Giants on Tuesday at AT&T Park. The Giants stayed alive in the division on Monday with a walk-off win in 12 innings.
If the postseason began today ... AMERICAN LEAGUE
Wild Card: Astros at Yankees
Division Series: Wild Card at Blue Jays, Rangers at Royals
Wild Card: Cubs at Pirates
Division Series: Wild Card at Cardinals, Dodgers at Mets
2015 POSTSEASON SCHEDULE
AL Wild Card Game: Oct. 6
NL Wild Card Game: Oct. 7
AL Division Series begin: Oct. 8
NL Division Series begin: Oct. 9
NL Championship Series begins: Oct. 16
AL Championship Series begins: Oct. 17
World Series begins: Oct. 27
Austin Laymance is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.