On a day full of games with playoff implications, it was the last swing of the night that had possibly the biggest impact on the standings.
Trailing by one, and down to their final out with nobody on base, the Dodgers rallied for two runs and beat the Cardinals, 4-3, on a Juan Rivera walk-off RBI single in the final game of the day. The victory pulled the Dodgers into a tie with the Cardinals for the National League's second Wild Card spot and also helped a slew of other contending teams.
With the Pirates and Brewers having already won earlier in the day, they pulled to within two and 2 1/2 games, respectively, of that now-shared Wild Card spot. The Phillies, despite a disappointing 5-0 shutout loss, remained just three games back, though they were leapfrogged by the red-hot Brewers.
In the American League, another walk-off hit dealt a devastating blow to the Wild Card-hopeful Angels. Zack Greinke turned in a masterful performance for the Halos, but they watched a 2-0 ninth-inning lead disappear as the Royals won, 3-2, after hitting back-to-back home runs off closer Ernesto Frieri.
Fortunately for the Angels, their 2 1/2-game deficit for the second American League Wild Card remained the same with the Orioles falling to the Athletics just a few hours after the Angels' collapse in Kansas City.
That Oakland victory also had an effect on a pair of divisional races.
Coupled with the Rangers' loss to the Mariners, the A's pulled to within two games of the AL West lead. As for the Orioles, they dropped to one game back in the AL East with Yankees' afternoon win over the Rays.
Tampa Bay remains three games back in the Wild Card hunt but fell to four games back in the division.
Nothing changed in the AL Central, as the Tigers took the field just minutes after the White Sox had finished off a 5-3 win over the Twins, and delivered a 5-3 victory of their own against the Indians. Chicago remains one game ahead of the Tigers.
Whether they admit it or not, teams are likely to be doing a bit of scoreboard-watching Sunday, with 12 afternoon contests having playoff implications.
In Los Angeles, though, the only scoreboard that matters for the Cardinals and Dodgers will be their own. After all, the winner of Sunday's series finale -- in which the Dodgers will be without Clayton Kershaw (right hip) -- will take sole possession of the NL's second Wild Card.
Back in the AL, the Yankees will take the field with sole possession of the AL East lead for the first time since last Monday. The Rays will be looking to win the rubber match and improve their own playoff odds.
Now back in second place in the AL East, the Orioles are just hoping to avoid a sweep at the hands of the A's in what would be the AL Wild Card matchup if the playoffs started today.
Sunday's key games to watch (all times ET)
Rays (Moore, 10-10) at Yankees (Kuroda, 13-10), 1:05 p.m. Preview >
Yankees will look to build on their lead in the AL East, while the Rays continue to battle in both the division and Wild Card races.
Reds (Latos, 12-4) at Marlins (Nolasco, 12-12), 1:10 p.m. Preview>
With just one loss in his last 10 starts, Mat Latos will look to help the Reds in their push for home-field advantage. They sit 2 1/2 games behind the NL-best Nationals entering play Sunday.
Phillies (Halladay, 10-7) at Astros (Lyles, 4-11), 2:05 p.m. Preview >
Roy Halladay, who hasn't lost since Aug. 15, hopes to help the Phillies bounce back from a disappointing shutout loss Saturday.
Angels (Haren, 10-11) at Royals (W. Smith, 5-7), 2:10 p.m. Preview >
The Angels will need to avenge a gut-wrenching, walk-off loss from Saturday in order to leave Kansas City with a series victory. Despite missing out on a quality chance to make up room in the Wild Card chase Saturday, the Halos still trail the Orioles by just 2 1/2 games for the second berth.
White Sox (Peavy, 10-11) at Twins (Diamond, 11-7), 2:10 p.m. Preview >
Jake Peavy will look to beat the Twins for the second time in 11 days as the White Sox go for a much-needed sweep at Target Field. Their lead in the AL Central remains at just one game over the pesky Tigers.
Mets (Young, 4-7) at Brewers (Peralta, 1-0), 2:10 p.m. Preview >
One day after surpassing the Phillies in the Wild Card chase, the Brewers aim to continue their sudden ascension up the NL Wild Card standings. Rookie Wily Peralta is 1-0 with a 3.00 ERA in two career starts.
Pirates (Locke, 0-1) at Cubs (Volstad, 3-10), 2:20 p.m. Preview >
After snapping their seven-game losing streak Saturday, the Pirates hope Jeff Locke can pick up his first career victory and help Pittsburgh cut into its two-game deficit in the NL Wild Card chase.
Tigers (Porcello, 9-12) at Indians (Jimenez, 9-16) 3:05 p.m. Preview >
Detroit hopes to extend its winning streak to five games Sunday, with a make-up game against the division-leading White Sox looming Monday. The Tigers sit one game back in the AL Central.
Mariners (Beavan, 9-9) at Rangers (Harrison, 16-9), 3:05 p.m. Preview >
Despite still holding the AL's best record at 86-59, Texas' lead over Oakland in the AL West has shrunk to two games.
Orioles (Wolf, 5-10) at A's (Straily, 2-0), 4:05 p.m. Preview >
The A's, now just two games back in the AL West, go for the sweep in a potential Wild Card preview. Baltimore trails the Yankees by one game in the AL East, but still hold a 2 1/2-game edge over the Angels for the second Wild Card.
Giants (Vogelsong, 12-8) at D-backs (Corbin, 5-7), 4:10 p.m. Preview >
The Giants have won four in a row but will need an improved performance from Ryan Vogelsong (10 ER over 8 1/3 combined innings in his last two starts) to extend the streak to five.
Cardinals (Wainwright 13-13) at Dodgers (Fife, 0-1), 4:10 p.m. Preview >
With ace Clayton Kershaw scratched because of lingering right hip pain, the Dodgers call on rookie Stephen Fife as they go for the series victory. The Dodgers and Cards enter the day tied for the second Wild Card spot.
Nationals (Gonzalez, 19-7) at Braves (Minor, 8-10), 8:05 p.m. Preview >
Looking to avoid another late-season collapse, the Braves will look to finish off a sweep of the division-leading Nationals. Washington still holds a 6 1/2-game edge in the NL East, while the Braves sit seven games ahead of the Cards and eight ahead of the Dodgers in the Wild Card chase.
If the postseason started today ...
Wild Card: Orioles at A's
Division Series: Yankees vs. White Sox | Rangers vs. Wild Card winner
Wild Card: Dodgers or Cardinals at Braves
Division Series: Reds vs. Giants | Nationals vs. Wild Card winner
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 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 »
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
Paul Casella is a reporter for MLB.com. Follow him on Twitter @paul_casella.