A smile crept across Adam LaRoche's face while he rounded the bases Tuesday night after hitting his career-high 33rd homer to become the third Nationals player with 100 RBIs in a season, another celebratory moment for NL East champion Washington during a 4-2 victory over the Philadelphia Phillies.

When the Nationals Park gates opened, early-arriving fans in the crowd of 33,546 were treated to a video montage of alcohol-spraying and general mirth-making from a night earlier, when the home team clinched its first division title since moving from Montreal in 2005.

Even the guy playing the national anthem on his bat-violin Tuesday wore a grey T-shirt marking the accomplishment.

Wednesday outlook:

For NL Central champ Cincinnati to secure home field advantage throughout the playoff, they will need a win and a loss from NL East winner Washington on Wednesday.

Otherwise, the Reds will be travelling to San Francisco on Saturday to begin the postseason.

Washington could end the suspense early, as they take on Philadelphia just after 1 p.m. ET on Wednesday. Cincinnati doesn't start against the Cards until seven hours later.

With a thick fog hanging over the stadium, Washington earned its major league-leading 97th win on a day when manager Davey Johnson decided most of his main guys deserved a rest. Indeed, LaRoche was Washington's only everyday player who stayed in for more than five innings — and he led off the sixth by driving the second pitch thrown by reliever Josh Lindblom (3-5) into the home bullpen in right field. Several Nationals relievers raised their fists as the ball cleared the wall.

LaRoche tied his career-best RBI total and joined Ryan Zimmerman and Adam Dunn — who each did it twice — as the only Nationals players to reach 100 in that category. Johnson and others greeted LaRoche with lots of vigorous high-fives and smiles; Jayson Werth pulled LaRoche in for a hug.

LaRoche responded to the fans' standing ovation by climbing to the top of the dugout steps and tipping his red batting helmet. In the seventh, some fans chanted "M-V-P!" before LaRoche struck out swinging.

His homer had put Washington ahead 2-1, and Steve Lombardozzi tacked on an RBI single off Lindblom, Philadelphia's third pitcher on a night both teams started relievers. Zach Duke (1-0) threw a scoreless sixth to get his first major league win since Aug. 14, 2011, for Arizona. Drew Storen earned his fourth save in five chances.

Phillies rookie Darin Ruf hit a pair of solo homers — off Tom Gorzelanny in the fourth inning, and Tyler Clippard in the eighth. All three of Ruf's homers in the majors have come against Washington.

Ruf led all minor leaguers with 38 home runs this year, earning the nickname "Babe."

Johnson used Gorzelanny to begin the game instead of originally scheduled starter Gio Gonzalez, preferring to let the left-hander who is 21-8 with a 2.89 ERA stay fresh for a start in Game 1 of the division series. Jordan Zimmerman is expected to start the second game.

LaRoche and centre fielder Bryce Harper were the only regulars in Johnson's starting lineup. He opted to sit third baseman Zimmerman, right fielder Werth, left fielder Michael Morse, shortstop Ian Desmond, second baseman Danny Espinosa and catcher Kurt Suzuki.

"I'm rewarding the guys that have been grinding through a tough schedule," Johnson said. "Sit back, gather your thoughts, we'll get back up tomorrow and go from there."

Harper, the NL rookie of the month for September, went 1 for 3 with a single and a stolen base, his 18th, in the fifth inning. Phillies manager Charlie Manuel came out to argue that Harper advanced on a ball fouled off by the batter. Manuel's third-place Phillies (81-80) will not make the playoffs, but the skipper wasn't going to let anything slide by.

Reds 3, Cardinals 1

Mat Latos won his fourth straight decision to finish the regular season and Scott Rolen homered off Chris Carpenter, helping the Cincinnati Reds keep the St. Louis Cardinals' post-season plans on hold for a couple of hours with a 3-1 victory Tuesday night.

St. Louis locked up the second wild card sport when Los Angeles lost later in the night against the San Francisco Giants.

The 37-year-old Carpenter (0-2) has a wealth of big-game experience and went 4-0 in the post-season last fall for the World Series champions, memorably outdueling Philadelphia ace Roy Halladay in Game 5 of the NL division series.

Injured most of this season, Carpenter made just his third start of the year gave up a pair of runs in the sixth to snap a 1-all tie. Bruce and Dioner Navarro had RBIs.

"I've said all along this is like my third spring training start in a key situation," Carpenter said. "I'm concerned about the stuff and the sharpness and tonight it was better than the last time.

"So, hopefully I get another shot."

Despite the loss, the Cardinals are 11-4 in their last 15 games. They'll draw Homer Bailey (13-10, 3.75 ERA), coming off a no-hitter at Pittsburgh, in the regular-season finale, with Adam Wainwright (14-13, 3.94) pitching for St. Louis.

"It's every pitcher's dream to pitch in the big moment," Wainwright said. "Hopefully the Dodgers will lose and we'll be able to go on our merry way. If not, I'm looking forward to the challenge."

If the Cardinals and Dodgers end up tied, a one-game playoff would be Thursday in Los Angeles, with the winner advancing to the wild-card game Friday in Atlanta.

Latos (14-4) had an abbreviated appearance while freshening up for the post-season and, like teammate Bronson Arroyo a day earlier, worked five innings and threw fewer than 75 pitches. Latos allowed a run on four hits with four strikeouts, all in a span of four at-bats against the bottom of the St. Louis lineup.

The 24-year-old Latos was 4-0 with a 2.27 ERA over his last seven starts and set career highs in starts (34) and innings (209 1-3).

"Pitching against a team like them, they're aggressive, they know what they're doing," Latos said. "A great hitting ballclub. To give up one run in five innings is doing pretty well."

With what was left of an announced crowd of 39,644 standing and hooting, Aroldis Chapman worked the ninth for his 38th save in 43 chances. He has allowed just one hit in four scoreless appearances covering four innings since returning from a nine-game absence due to shoulder fatigue on Sept. 21.

Carpenter gave up three runs and seven hits in six innings while losing for the fifth time in 19 career decisions against Cincinnati. He had seven strikeouts, two more than his total for the first two starts over 11 innings.

The Cardinals stranded two runners in the second and third against Latos and had two on with one out in the seventh before Sean Marshall got pinch-hitter Shane Robinson to fly out and Jon Jay on a broken-bat groundout.

Rolen, batting .247 but hitting at a .301 clip since the All-Star break, tied it in the fourth when he jumped on a first-pitch hanging breaking ball for his eighth homer.

Baker played for keeps in the early going. He brought the infield in with a runner on third and one out in the first for Matt Holliday, who hit a sacrifice fly, then intentionally walked eighth-place hitter Pete Kozma with two outs and a man on third in the second inning to get to Carpenter, who grounded out sharply to