The Philadelphia Eagles have every reason to play an outstanding game today. The Redskins have every reason to produce a "Gong Show" clunker.

The Eagles, losers of two straight and four of their last seven games, know that if they don't win this 1 p.m. game at RFK Stadium (WDVM-TV-9, WMAL-Radio-63), their chances of repeating as NFC East champs are all but over. That's why many of the players consider this to be their most important game since last January's Super Bowl against Oakland.

Last Sunday in Buffalo, the Redskins saw their longshot playoff hopes wiped out with the help of five turnovers and nine penalties. Spirits were low most of the week at Redskin Park and Coach Joe Gibbs said he will be watching carefully today "to see who plays hard and who doesn't. That would have to influence me in the future."

Yet these are the kinds of circumstances that sometimes produce the most surprising upsets, one of the reasons Eagle Coach Dick Vermeil has had a short fuse and a long face since losing to Miami Monday night. His 9-4 team, which trails the Cowboys by a game in the NFC East race, plays at Dallas next Sunday.

There is no similar pressure on Gibbs or his players, who are four-point underdogs. What he will emphasize today is that his players should relax, enjoy themselves and try to take advantage of the last opportunity this seaon to beat a team with a winning record.

"We'd like to have a win over a sure playoff team," he said. "It would help us measure our progress. We'll be able to see how far we really have come since losing to them in September."

The Redskins have had problems figuring out what to expect from Philadelphia. The Eagle defense, the best in the NFL, is playing superbly. But the team's offense, so efficient last season en route to the Super Bowl, has been dreadful lately, scoring only 20 points the last two weeks.

Washington's defense sometimes seems vulnerable enough to surrender 20 points in a quarter. Philadelphia likely will follow a familiar attack pattern: sweeps around the Redskin right side mixed with long passes against the nickel alignment. Five backs in the past six weeks have gained at least 100 yards running against the Redskins, and some of them weren't nearly as good as Philadelphia's Wilbert Montgomery.

The return of cornerback Lemar Parrish, who has missed three weeks with a sore knee, should help the Washington pass defense, which limited Buffalo's Joe Ferguson to 41 net yards. Jeris White will continue to start for Parrish, who will be used in nickel situations.

The Redskins should benefit from the Eagles' lack of receiver speed. Harold Carmichael remains an imposing target, but Philadelphia has had little luck throwing deep this season.

When these teams first met in September, the Redskins gained 337 yards and outplayed the Eagles for 50 minutes before turnovers led to a fourth-quarter collapse and a 36-13 Philadelphia win. Montgomery didn't play in that game, nor did Joe Washington, Russ Grimm, Monte Coleman and Brad Dusek for the Redskins. And George Starke was hurt on the game's first series.

Gibbs' team is much healthier now, but it is still haunted by turnovers against superior opponents. Two telling statistics: 14 of the Redskins' 18 interceptions and 11 of their 19 lost fumbles this season have come in games against likely playoff participants.

Now they must try to solve a defense that leads the league in fewest points surrendered (185) and has given up more than 20 points only once this year. Opponents are averaging only 104 yards rushing and 176 passing, figures the Redskins often have matched in the first half of games the past seven weeks.

"They are as well-coordinated and as well-coached as any defense you'd want to see," quarterback Joe Theismann said. "To be successful against them, you have to limit your mistakes. You have to take the approach that you can't afford any turnovers and that when you have an opportunity to make a big play, you have to take advantage of it."

Theismann directs an offensive unit that is ranked sixth in the NFC, an impressive achievement considering the Redskins lack a full complement of talented wide receivers, have been plagued by injuries to an inexperienced line and have lost Joe Washington (their leading receiver and runner) for the equivalent of four games.

The lack of depth at receiver has been most telling in games against quality defenses. Opponents double up on Art Monk, concentrate on defending Joe Washington and then dare Theismann to throw to Virgil Seay, Terry Metcalf or Ricky Thompson.

Still, Theismann has recovered from a shaky start to threaten all of his single-season passing bests. He needs only 105 yards today to become the fourth passer in Redskin history to reach the 3,000-yard plateau. With 20 more completions and 39 more attempts, he will top his previous highs of 454 and 262, respectively.

Either Booker Russell or Billy Campfield will start at fullback for the Eagles, replacing injured Hubie Oliver . . . John Bunting, who missed the Miami game, will start at linebacker . . . The Redskins will continue to use Dallas Hickman at defensive end on obvious passing situations . . . Washington has lost three straight and five of the last six to the Eagles.