Halfback Joe Washington's damaged rib cartilage has healed enough so he can start at Buffalo Sunday, Coach Joe Gibbs of the Redskins said yesterday.

Gibbs' optimism about his star runner contrasts sharply with news from Buffalo, where Coach Chuck Knox says it's unlikely his best runner, halfback Joe Cribbs, will be able to play against the Redskins.

Although Knox has refused to rule Cribbs out, he says it is probable Cribbs won't play. Cribbs, who has fractured ribs, has not practiced this week.

Gibbs said that Washington will start, barring further damage to his ribs. The Redskins plan only a light workout today before leaving for Buffalo.

"Since it's an injury brought on by the twisting of his body, he could hurt it anytime, even in warmups," Gibbs said. "But right now, he'll start as long as he doesn't get worse. It really will be up to him. If he tells me he can go, he'll go.

"The major question now is, how long it (the rib) will hold up."

When Washington was hurt Sunday in the first half of the Dallas game, it seemed unlikely he could play again so soon. Even Gibbs admitted he was preparing a game plan that excluded Washington.

"It seemed like an injury that would take a week or more to heal," Gibbs said. "Joe has got a high pain threshold. It hurts, but he's a tough person. He wants to play. He's told me that all along."

The Redskins have made other lineup changes. Receiver Virgil Seay, who has been out two weeks with a pulled hamstring, will start, as will guard Melvin Jones, who has been out with a pinched nerve in his neck. Monte Coleman and Brad Dusek will swap linebacker spots, Dusek going to the right, Coleman the left.

Washington's presence in the starting lineup is essential for the Redskin offense, especially against a Buffalo defense which has not allowed a rushing touchdown the last six games. The Bills are ranked second overall on defense in the American Football Conference.

"They play a lot like Philadelphia's (3-4) defense," Gibbs said. "They are very solid, very aggressive and they don't make mistakes. Teams have run on them, but they don't ususally give up a lot of points."

Buffalo has had problems with NFC East backs. Ottis Anderson, Tony Dorsett and Wilbert Montgomery have gained more than 100 yards in games against the Bills, who lost all three games. Joe Washington has had one 100-yard game this season and was 16 yards short of another against Dallas before getting hurt.

The absence of Cribbs would benefit the Redskin defense greatly. Cribbs is the type of quick runner who has given the Redskins considerable difficulty the last five weeks.

In that span, four backs have gained at least 100 yards against the Redskins, and Defensive Coordinator Richie Petitbon expects Buffalo to come out running, Cribbs or no Cribbs.

"His replacement, Roland Hooks, isn't a bad athlete, either," Petitbon said. "But Cribbs is special. He makes big plays. But why wouldn't you try to run against us this season?"

This has been a frustrating year for Petitbon. He never touted his unit as outstanding, but had expected a lot more consistency. Injuries, subpar performances and lack of quickness have led to struggling efforts recently and, at times, the Redskin defense has played as poorly as almost any defense in the league.

Petitbon has been the first to admit after some games that, as he put it last week, "We stunk." But he said yesterday he still believes his unit can play well, if it causes turnovers.

"Let's face it, we haven't been playing as well as we want to," he said. "We haven't had a pass rush, our coverage has been spotty at best, and our linebackers have been hurt so much we've had to shuffle people. The result has been inconsistency. We've been lacking; no doubt about it.

"A team like Buffalo will move the ball on us, but our guys are still playing hard enough. We still are getting enough really good effort to force mistakes. If we don't, then we don't hold up our end of the bargain. When those chances come . . . we can't flub them, like we did by dropping all those passes against Dallas."

When the season began, Petitbon planned free substitution, similar to that used by former coach Jack Pardee. Injuries precluded that approach, curtailing the team's down-and-distance specialists.

Since defensive end Coy Bacon was cut because of disciplinary problems, there has been little or no pass rush. Quarterbacks have had more time to throw, negating Petitbon's pet blitzing strategy and hurting the secondary's coverage.

Knee problems have hindered Lemar Parrish, the team's best man-to-man defender. That has hurt the team's blitzing and coverage. When the Redskins blitz, the cornerbacks often are left with single coverage, making Parrish's skills even more valuable.

"Toss in the fact that Monte Coleman has been struggling all year with injuries, and we just haven't been able to build from a solid foundation," Petitbon said.

The Redskins nearly made Cribbs their No. 1 choice in 1980, before finally opting for receiver Art Monk . . . . Buffalo lineup changes: fullback Roosevelt Leaks for Curtis Brown, and linebacker Phil Villapiano for injured Chris Keating. Either Conrad Dobler or Jim Ritcher will start at guard.