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 gray T-shirt marking the accomplishment.
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.
LaRoche and center 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.
If he's displeased about the way 2012 went for five-time defending division champion Philadelphia, at least Manuel can get excited about what Ruf is doing so far.
"I like what I see out of him as far as the ball jumping off his bat," Manuel said before the game. "He's got power. He's got power to all fields."
NOTES: Johnson said RHP Jordan Zimmermann will start Game 2 in the playoffs. Either RHP Edwin Jackson (9-11), pitching the regular-season finale against Philadelphia on Wednesday, or LHP Ross Detwiler (10-8) will take Game 3, depending on the opponent. ... LHP Cliff Lee (6-8) starts for the Phillies on Wednesday. ... LaRoche hit 32 homers for Atlanta in 2006, and drove in 100 runs for Arizona in 2010. ... Washington's Mark DeRosa made his first start at shortstop since 2006 for Texas. He was charged with a fielding error in the third. ... Coming to a blooper reel near you: Phillies RF Domonic Brown completely misjudged his leaping attempt to catch pinch-hitter Desmond's deep foul fly in the eighth - and the ball landed quite a ways behind Brown. ... The Teddy Roosevelt entry in the Presidents Race once again failed to win, drawing a smattering of boos.