Although the Washington Redskins have clinched a playoff berth, they still have a scroll's-length list of reasons why they must beat the St. Louis Cardinals today at RFK Stadium.

The foremost reason is that the winner of today's game will win the NFC Eastern Division title, a bye in the wild-card playoff round and the home field advantage in the division playoff game. The Redskins are 6 1/2-point favorites in the game (WDVM-TV-9, 1 p.m.).

The stakes are a bit higher for St. Louis, 9-6 with a three-game winning streak. If the Cardinals lose, they would be eliminated.

Jim Hart, the Redskins' reserve quarterback who spent 18 seasons with St. Louis before this season, said this will be the Cardinals' biggest game since 1975, the last time they won the division title.

And Cardinals quarterback Neil Lomax concurred, saying, "Three weeks ago, I'll be honest with you, I figured we were probably out of it (with a 6-6 record) . . . This could be our last game of the season."

Linebacker E.J. Junior said, "This is our Super Bowl."

If the Redskins win, they would play at RFK Stadium Dec. 29 or 30 against either the Los Angeles Rams or the Chicago Bears in a division playoff game.

If the Cardinals win, the Redskins would be reduced to being a wild-card entry and would play either Dallas, the Giants or the Rams next Sunday at RFK Stadium.

Not only are these Redskins thinking playoff, they are thinking layoff. Coach Joe Gibbs said the Redskins could use a bye in next Sunday's wild-card round.

"It would be tremendous for John (Riggins, the fullback)," Gibbs said. "If he could spend a week at the hospital, resting, think of the difference it could make."

Riggins, 35, returned to Redskin Park yesterday after spending two days in traction at Sibley Memorial Hospital to help reduce pain in his lower back and hips. He participated in a walk-through practice, reviewed films yesterday afternoon and is listed as "probable" (75 percent chance he will play) today.

"If I had to guess," Gibbs said, "I'd say that John will start and then we'll see what happens."

Make no mistake, one thought is central to the Redskins: they very likely might be just two victories away from playing San Francisco at Candlestick Park in the NFC title game, for rights to appear in their third consecutive Super Bowl. (The 49ers, as Western Division champions, need just one victory to reach that conference title game.)

Redskins emotion will be fueled for other reasons today. Players have talked all week about how they hope wide receiver Art Monk (95 receptions) catches seven passes to break the league's single-season mark of 101 receptions set by Houston's Charley Hennigan in 1964.

They have talked, too, about how they hope the defense sacks Lomax at least five times. That would allow the Redskins, with 63 sacks, to break the league's single-season record of 67 set by the Oakland Raiders in 1967.

And these Redskins have remembered how the St. Louis players reacted after Neil O'Donoghue kicked a 21-yard field goal in the final moments of the Cardinals' 26-24 victory Oct. 21.

"That's the one thing that sticks out in my mind," tight end Don Warren said. "I remember how they ran in front our bench and all of them were flashing No. 1 signs in our faces. Since I've been here, I've never been taunted like that."

To a man, the Cardinals now say that they meant no harm. "I wasn't any part of that. I think the guys were just so excited about beating Washington," Lomax said. "I don't think it meant we hate or disrespect the Redskins . . . We just got a little carried away probably."

The memory seemingly has left Redskins spirits smoldering. Special teams captain Pete Cronan said, "Getting beat by those guys is a pride thing now. This game is for the division title and for bragging rights. Losing to them a second time would be like calling my mother a bad name."

In that game, Lomax, voted an all-pro for the first time this season, threw for 361 yards and three touchdowns, helping the Cardinals overcome a 21-10 third-quarter deficit. Wide receiver Roy (Jet Stream) Green caught 166 yards worth of passes, including two for touchdowns (38 and 83 yards).

The Cardinals rushed for 120 yards, 75 by running back Ottis Anderson. Their defense made enough changes to disrupt the Redskins' offense.

Often, the Cardinals blitzed with linebackers and safeties. They deployed a five-man defensive front at times. They held Riggins to 98 yards on 32 carries and quarterback Joe Theismann was sacked four times and completed only slightly more than half his passes. (Theismann now has a streak of 12 consecutive games in which he has thrown at least one touchdown pass.)

The Redskins say they expect the Cardinals to blitz often again today. "They were successful with it last time," center Rick Donnalley said. "Teams usually stay with things that are successful."

The Cardinals won't be helped any by the absence of veteran left guard Terry Stieve, who suffered a fractured fibula in the Cardinals' 31-21 victory over the New York Giants last Sunday. Stieve, expected to be out three to four weeks, will be replaced by rookie Doug Dawson, who must face defensive tackle Darryl Grant (career-high 7 1/2 sacks).

"I think we'll find out how hungry we are to get a third division title," Gibbs said. "Are we fat and sassy or are we for real?

"The first time you win, it's great. After a while, though, it seems like the thrill and excitement isn't there. No stadium is like our stadium. We need our place back at a fever pitch."