Doug Williams hasn't been the Washington Redskins starting quarterback very long, yet he has come to realize that the receiving corps he works with is in a constant state of flux.

"It ain't a matter of who's the receiver," Williams said yesterday at Redskin Park. "It's a matter of who gets the job done."

With veteran Art Monk definitely out with a knee ligament injury, Gary Clark, Ricky Sanders and Anthony Allen are the three wide receivers who will run under Williams' passes beginning Sunday at 12:30 p.m. when the Redskins play the Chicago Bears at Soldier Field in an NFC semifinal game.

Clark and Sanders have been around the entire season; Allen arrived during the strike, disappeared for most of the rest of the season, then emerged at season's end. He is the Redskins' not-so-secret weapon for Sunday's game. Coach Joe Gibbs wanted to keep Allen's presence in the Redskins' plans a secret. Word got out, but Gibbs still isn't saying if Allen will play.

Nonetheless, he is expected to. If the temperature and wind speeds are right for passing, Allen figures to catch his first passes since the replacement games in October. He was a star then, making 13 receptions for 337 yards, a healthy 25.9-yard average. His 88-yard touchdown pass from quarterback Ed Rubbert in the first replacement game against St. Louis was the longest touchdown catch of the season in the NFC.

"When we were off during the strike, {Allen} produced very well," Clark said yesterday.

Allen should be as visible at Chicago as Sanders was during the early part of the season, when he was the No. 3 receiver behind Monk and Clark. Clarence Verdin took over that spot when Monk was injured Dec. 6, but he has been replaced by Allen for the playoffs, Verdin has said.

"I'm tickled to death," Allen said. "Truly, I am. This time of the year, in the playoffs, it's really something special."

Gibbs has closed Redskins practices to the media, which means few know what the Redskins plan to do against the Bears. Allen knows, of course, and gave a rough outline yesterday.

"How much I play depends on the weather, how the game goes," he said. "It depends on whether we're down, how bad the weather is, whether you can throw at all or not, whether you're going to go to three tight ends and run the ball all day.

"If it's a regular clear-cut day, then I'm sure I will play a lot. Especially against the Bears, trying to spread them out."

As good as Allen looked during the strike, he is not Art Monk. Neither are Clark or Sanders, for that matter. Most importantly, they are not as big as Monk. He is 6 feet 3; Sanders and Allen are 5-11, Clark is 5-9.

"Art's extremely good at being inside," Gibbs said. "He was a big target. It's exceptional in today's football for a receiver to be that big. A lot of routes he caught inside. When you lose somebody like that, it's tough to make up in your offense."

Clark has run those inside routes of late and seems to have made the adjustment to being the team's No. 1 receiver. He says the changes in the receiving corps, and the changes at quarterback, have not been difficult to play around. Two seasons ago, Joe Theismann said he and new receivers were getting their signals crossed now and again. Clark said there have been no communications problems this time.

"The way our practices work, Ricky and Anthony had a chance to work with Doug before he became the starter," Clark said. "There hasn't been any change we've had to make. I haven't had to make any change at all."

Although he is unknown to most fans, Allen has played in the pros for five seasons. He had stints with six U.S. Football League teams and the Atlanta Falcons. Under then-head coach Dan Henning, Allen caught 24 passes for 363 yards and four touchdowns. He started the opening game of the 1986 season, but missed most of the year with a knee injury.

When the NFL players went on strike, Henning, now an assistant with the Redskins, suggested to Allen that he might want to cross the picket line and come to the Redskins. Allen had told several teams "no," but decided just four days before the first replacement game to join Henning and the Redskins.

It was a wise choice. In that game, he set a team record with 255 receiving yards and immediately earned the respect of fellows named Clark and Sanders, who call their new-found friend "Double A."

"I saw the final quarter," Sanders said. "He looked good."

"There are no hard feelings," Clark said. "It helped him get a job here. It worked well for him."

When the strike ended, Allen stuck around, practicing with the scout team until he was released Nov. 28. But, 10 days later, he was re-signed when Monk was injured. He had an offer to join Tampa Bay and perhaps start for the rest of the season, but Allen decided to come to Washington and ride the bench.

"If I'd gone somewhere else, I wouldn't be in the playoffs now," Allen said.

He finally made the active, 45-man roster for the regular season finale at Minnesota, but he did not get into the game. Now, he not only will be activated, he should play.

"I know it took a lot to make the decision to let me play," Allen said. "I haven't played in however many weeks. And when it's on the line and means the most, to call on me, I'm sure the coaches do have faith in me."

Strong safety Alvin Walton (sprained right ankle) returned to practice yesterday and "took everything," Gibbs said. No one else is injured and everyone practiced, he said.

The team has some roster moves to make by Saturday. Tops on Gibbs' list are tight end Clint Didier (groin) and running back Keith Griffin (thigh). "We'd like to have Clint up for sure," Gibbs said. "We'd like to have Keith up. We'll just have to wait and see . . . So much is up in the air. There are 10 different ways to go. We will wait until the end {of the week}." . . .

Will cornerback Darrell Green return punts Sunday? Gibbs is keeping that a secret, but Chicago Coach Mike Ditka isn't, announcing to reporters Green will be the Redskins' punt returner.

Gibbs: "It just depends how much we want to use him."

Green: "I'm not commenting."