Rookie running back Keith Griffin admits he has been looking over his shoulder all week, just in case John Riggins showed up for the Washington Redskins' practice.

But, once again, Riggins did not practice yesterday. He did make a brief appearance -- wearing sweat pants, a heavy jacket and his locker room slippers. But he wasn't about to partake in Riggo Drill drills.

Riggins has not practiced all week because of continued pains in his lower back, and trainer Bubba Tyer confirmed yesterday Riggins also is suffering from hemorrhoids.

Consequently, the 35-year-old fullback, who is just 46 yards short of the fifth 1,000-yard season in his 13-year career, was downgraded yesterday from probable to questionable on the team's injury report. That means there is a 50-50 chance Riggins will not play Sunday against the Detroit Lions at RFK Stadium.

The most definitive word came from Coach Joe Gibbs, who said after practice, "The odds are we will go without John."

Of course, Gibbs will not count out Riggins. He said Riggins, who talks to the press only after games, told him yesterday he will try to warm up before the game.

But the fact is, Gibbs hasn't seemed so uncertain of Riggins' status on a Friday of any other week this season. "I'm not trying to jerk anybody around here," Gibbs said. "I'm not trying to keep the other team guessing who will play for us . . . This is the farthest John has gone without practicing. The decision will be up to John on Sunday."

Which brings us to Griffin, a 5-foot-8, 185-pounder who, Gibbs said, would replace Riggins in the Redskins' one-back offense if needed.

Only Tampa Bay's James Wilder (249) has more carries this season than Riggins (247). Griffin has rushed for 148 yards on 30 carries, but has run only three times for six yards the last three weeks. Otis Wonsley, usually Riggins' blocking back on short-yardage and goal-line plays, would spell Griffin if Riggins doesn't play.

Fumbles have been a problem for Griffin. "That's one reason I really want to play in this game -- to show people that I can hold on to the ball . . . I feel like I can run the ball inside. My size is an advantage because people hit me high," he said.

The last time Riggins missed a game was against Detroit in October 1983. The Redskins won that game, 38-17, when Joe Washington rushed for a career-high 147 yards on 22 carries.

Griffin said Gibbs reminded his running backs during team meetings this week of Washington's 147-yard performance against Detroit. Sort of putting the possibilities in place.

"I would have hoped that Keith would have played more by this point," said Don Breaux, coach of the running backs. "He put the ball on the ground a couple times and because John (Riggins) hardly ever fumbles, it sort of magnified the problem for Keith. But it's not like Keith does it all the time. We have confidence in him."

Of course, all the Redskins have opinions of what Riggins' absence would mean.

Center Rick Donnalley: "What can we do? Play whoever is healthy. Everybody will have to bear down even more in short-yardage plays. (Riggins) is the best short-yardage runner in the game . . . When he's on the field, he gives us confidence."

Breaux: "You know the water will never get too hot for John. He will always do his part. He likes to call it 'loading the wagon.' You lose probably the best short-yardage and goal-line runner of recent times. You lose a guy who has done it."

Right tackle Mark May: "We would lose the consistency of having a fullback for 30 or 40 times a game . . . (But) if it comes down to the point where the game is close, John will be there no matter how much pain he is in. That's the type of person he is. Whoever steps in for him will just have to be the hero."

Tight end Clint Didier: "We could get down about him not playing, but I don't think we will. All of the other people will fill in and maybe our offense will be even better. It's an attitude thing. I think we'll be ready for the situation at hand. And John's been known to fool some people. You never know, he may be out there."

Didier has been playing with greater frequency the past three weeks, usually replacing Rick Walker at the H-back (motion tight end) spot.

In his five games since reactivation from injured reserve, Didier has caught 11 passes for 129 yards and three touchdowns. Walker has caught five for 52 yards and one score.

"We've been forced into situations early in the game over the last three weeks," said Warren Simmons, the tight ends coach, "where we've gone with Didier more for the passing game. Didier is a viable force for us. We sat both guys (Didier and Walker) down this week and told them their roles.

"Rick does more things blocking for the run and he's good running the ball after catching short passes. Clint's more of a deep threat . . . I think Rick understands that Clint's got a lot of talent. We really think Rick does a lot of things for us. We're not crossing him off the list by any means.

"We went to two Super Bowls with Rick. Clint has had problems with injuries and Rick has been nicked a little, too. This way (by alternating), we can keep both guys healthy . . . We also think of Clint as being a third receiver."

Walker, an eighth-year player, said, "My objective is to win. Whatever (platoon) system puts more money in my pocket is fine by me. Right now, we're not setting the world on fire on offense. People are adjusting. Things are happening . . . I don't think this is a demotion; a demotion is when you play bad or drop a ball. That hasn't happened. I just think that Clint has got some great skills."

Didier, a third-year pro, said, "We sort of knew our roles before (the coaches talked with them). Ricky's more run-oriented. I'm more pass-oriented. But I want to improve my blocking, too."