WASHINGTON -- The Nationals closed down RFK Stadium on Sunday, playing the type of tough, hard-nosed baseball that has made them a significant factor in determining whether their National League East division foes -- the Mets and Phillies -- will make the playoffs.

As the schedule would have it, the Nats will finish the season with six games against those two clubs, including three against the Mets at Shea Stadium, beginning on Monday night, and another three against the Phillies at Citizens Bank Park during the season's final weekend.

"It does feel good, because these last six games are really important," said closer Chad Cordero, who tossed the ninth inning of his club's 5-3 win, thus ending the Nats' brief three-year stay at RFK and hindering the Phillies' drive to the playoffs. "We have to go out there and play hard, because those teams are shooting for a playoff spot. We just can't lay down because we're already out of it. Any win we get is going to make us feel good."

The Nationals have already made a dent. They were 3-4 against the Mets and Phillies during their final RFK homestand, defeating the Mets twice and giving the Phillies fits in four games. Philadelphia could have lost three of them, but it instead came out of it with three critical victories before losing on Sunday.

The Phillies came back from a 6-2 deficit to win 7-6 on Thursday night, and they had a relatively easy go of it on Friday night before prevailing with three runs in the 10th inning on Saturday. They went into Sunday's action trailing the Mets by 1 1/2 games in the NL East and the Padres by just a half-game in the NL Wild Card race. The Nats weren't to be defeated amidst the hoopla of their RFK finale on Sunday.

"This was the big one," Annette Lerner, the wife of Ted Lerner, the team's principal owner, said on the field after the game. "We wanted to close this ballpark on a high note. I'm exhausted. This game was so emotional."

With the Mets winning in Miami and the Padres losing at home to the Rockies, Philadelphia dropped to 2 1/2 games behind New York and remained a half-game back of San Diego. Even the Rockies have closed within 1 1/2 games in the wild, wild NL Wild Card race after sweeping the Padres this weekend at PETCO Park.

The coming week won't get any easier. The Phillies are attempting to make the playoffs for the first time since they lost to the Blue Jays in the 1993 World Series. And the Mets are trying to avoid a late-season collapse hastened by seven consecutive losses to the Phillies. Anything short of making it to the World Series for the Mets, who lost a seven-game NL Championship Series to the Cardinals in 2006 that came down to the last pitch, would be considered a disaster.

As the Mets take on the Nats on Monday to Wednesday nights at Shea, the Phillies will play the Braves at home on Tuesday to Thursday nights. The Mets, who have seven games left (all at home), play a makeup game on Thursday night against the Cardinals and finish with three against the Marlins, while the Nats attempt to stomp out the Phillies.

Out west, the Padres play three games in San Francisco from Monday to Wednesday nights and a four-game set in Milwaukee to finish up the season. And the Rockies have three games in Los Angeles before finishing at home with three against the Diamondbacks, who lead the Padres by 2 1/2 games in the NL West.

Nothing is certain and, at the moment, the combinations are dizzying. Of course, for the next three days at least, Phillies manager Charlie Manuel is rooting for the Nationals as they take on the Mets.

"I'd rather be playing head-to-head against the teams we were competing against at this time of the season," Manuel said. "You can get eliminated quick, but playing these other teams, you just don't control your own fate. Like, when we win and the Mets win and San Diego wins, it's hard to catch up. The Nationals -- my goodness, they've been tough. They can have their say before it's all over, no doubt. Hopefully, they have their say against the Mets."

The Nationals, as a group, have stayed away from calling themselves spoilers.

First-year manager Manny Acta noted that he's really involved in his "own little race," staying out of the NL East cellar for the first time since the team moved from Montreal for the 2005 season. After Sunday's action, the 69-87 Nats lead the Marlins by three games.

"It could be San Diego, it could be Colorado, it could be Pittsburgh, we're just trying to get wins," said catcher Brian Schneider, one of only six players remaining from the Expos days.

A 4-2 record in the season's final week will not only jostle what the Mets and Phillies are attempting to do, but it will secure fourth place and a season with fewer than 90 losses. Both are significant accomplishments considering that during Spring Training, most experts projected the Nats to have an historically losing season.

"Hey, I hope I go unbeaten the rest of the way," Acta said. "I couldn't care less who makes it [to the playoffs] or doesn't make it. I just want to win as many games as possible, regardless of whether it's against the Phillies or the Mets."