ST. LOUIS (AP) -- Michael Morse circled the bases for a grand slam after taking an imaginary swing, and the Washington Nationals cut their magic number for winning the NL East to one Saturday night, beating St. Louis 6-4 on Kurt Suzuki's two-run double in the 10th inning.
The Nationals have put on hold a champagne celebration until they win the division, and were forced to wait at least another day when second-place Atlanta beat the Mets 2-0.
Washington had already assured the nation's capital of its first postseason appearance since 1933. The Nationals can win their first division title on Sunday when a St. Louis native, lefty Ross Detwiler, starts against Cardinals 17-game winner Lance Lynn.
St. Louis' magic number for clinching the second NL wild-card spot remained at three.
The Nationals opened the game with a blast, and a bit of comedy.
Bryce Harper singled, Ryan Zimmerman doubled and Adam LaRoche drew a full-count walk to load the bases in the first inning.
Morse hit a line drive on the first pitch that cleared the right-field wall and landed in a grassy section beneath a video board. First base umpire Chris Guccione didn't see it, however, and play continued. Right fielder Carlos Beltran made a relay to second baseman Skip Schumaker, who ran down Morse as he retreated toward first.
The umpires looked at video replays and confirmed it was indeed a home run. The umps ordered all runners to retrace their steps and put Morse back at the plate, where he mimicked his swing minus a bat and then made his trot.
Morse has four career slams and two this season. He is 6 for 11 with 14 RBIs with the bases loaded this year.
Pete Kozma had three hits and two RBIs for St. Louis. He scored on Jon Jay's sacrifice fly off Drew Storen (3-1) in the ninth to tie it.
The Nationals got a pair of walks and a passed ball to set up the go-ahead hit, a double off the wall in left-center by Suzuki, who's batting .385 with runners in scoring position.
LaRoche walked for second time to open the 10th against rookie Sam Freeman (0-2) and also had a pair of hits.
Craig Stammen allowed a hit but also got a double-play ball in the 10th for his first save in two chances.
Just like a night earlier when the Nationals' Edwin Jackson trailed 5-1 after an inning, Cardinals starter Kyle Lohse got into deep trouble early.
Nationals starter Jordan Zimmermann entered 0-2 with a 10.71 ERA in four starts against the Cardinals, allowing at least five runs each time. He retired eight of nine to open the game and before the seventh had allowed only one runner into scoring position.
The Cardinals got three straight one-out hits to chase Zimmermann in the seventh, singles by Beltran and Skip Schumaker ahead of a two-run double by Kozma, the eighth-place hitter. Jay added an RBI single off Sean Burnett to cut the deficit to one.
NOTES:(at) The blown save was Storen's first in four chances. ... Cardinals 3B David Freese missed his fifth straight start with a sprained right ankle but could play Sunday. Matt Carpenter subbed for him again Saturday. Freese drew a five-pitch walk as a pinch hitter in the seventh. ... Beltran, who entered in a 3 for 21 slump, batted sixth for the second straight night and fourth time overall this season. He's been the primary cleanup man and has 92 RBIs, but just 27 since the All-Star break.