The Washington Redskins have spent this week saying they expect the Philadelphia Eagles to win at Phoenix this afternoon, and that they're prepared to pack their bags for a trip next weekend to Veterans Stadium.

That's the conventional logic, but yesterday, as they settled on a series of roster moves to be announced today, their decisions indicated they believe there actually might be something on the line in Sunday's game against the Buffalo Bills at RFK Stadium.

That would be the case only if the Eagles lose to the Cardinals this afternoon, because a Philadelphia victory ensures that Eagles-Redskins III will be played at Veterans Stadium when the NFL playoffs open next week.

But if the Eagles lose to the Cardinals, the Redskins will get the wild-card game at home by defeating the Bills.

Perhaps with that in mind, the Redskins decided to use both their final free roster moves to add running back Gerald Riggs and defensive tackle Tracy Rocker to the 47-man roster today.

In addition, with an eye toward the Eagles, the Redskins made a preliminary decision to activate quarterback Stan Humphries next week when they get an additional free move for the playoff game.

And they haven't given up on the possibility that defensive tackle Eric Williams might be ready for the playoffs. Williams will remain on the 47-man roster, and another evaluation of his injured left foot will be made next week.

"He has made so much progress that you don't want to give up too quickly," said General Manager Charley Casserly. "If there's any way to have him out there, we want him."

He's definitely out of Sunday's game, as are running back Kelvin Bryant (sprained knee), defensive end Markus Koch (sprained knee) and cornerback Sidney Johnson (concussion).

Bryant will be placed on injured reserve to make room for Riggs. In fact, there is a good possibility that Bryant's star-crossed, five-year career with the Redskins is over.

He has been used sparingly and was sidelined by injuries every season. He has 26 catches this year, but has really been utilized only down the stretch, catching 19 passes the last eight games.

Now, rookie Brian Mitchell will have a chance to play in some of those third-down situations, and how he looks may decide whether Bryant is offered a contract for 1991.

Bryant certainly won't be protected under the Plan B free agency system and likely will get some offers from other teams. If he doesn't, he still could return to the Redskins because Coach Joe Gibbs thinks highly of him on both a personal and professional level.

To activate Rocker, the Redskins apparently will release a player who probably will be re-signed next week when current No. 3 quarterback Gary Hogeboom is released. Hogeboom was signed in Week 3 after Mark Rypien was hurt, and will be expendable when Humphries returns.

Riggs will be used strictly as a backup to Earnest Byner, but Gibbs is excited about having him back in uniform. He hasn't played since spraining his left arch in Week 9 in Philadelphia, but when healthy he's looked as good as ever.

"He could give us a great lift right now," Gibbs said. "Not many people have that kind of guy coming back at this point in the season."

Rocker hasn't played since Week 7. He was placed on injured reserve after the Redskins' second loss to the New York Giants. Team officials at the time said he had a sore knee, but the move also came a few days after he jumped offside in a key situation against the Giants.

His return will give the Redskins six healthy defensive linemen and provide insurance in case end Charles Mann is unable to go the entire game. Mann missed a third straight day of practice yesterday with a sore right knee. He said he'll play on Sunday and that he hopes to be back at full practices next week.

But he also revealed that he'll probably undergo offseason surgery to have debris removed from the knee. Mann said the sore knee was no excuse for his sub-par season -- his sacks are down from 10 to 5 1/2 and he was credited with no tackles last week against Indianapolis -- but admitted that it has bothered him almost all year.

He said the sore knee "is no alibi. I don't need one. But I've hurt it a couple of times. I had a guy fall on the back of my leg a couple of weeks ago. I didn't practice all week but did play in the game. You're not going to be as sharp as you'd like. Then to get it hyperextended is tough. If that happens to a good knee, it's going to hurt you. This is a knee that has been operated on. It's tough enough going through the physical pounding regularly, but to have some things happen when it's already bothering you makes it worse."

Humphries has believed for several weeks he might play again this week, although at one time, Gibbs favored activating return man Walter Stanley instead. But there are many reasons for picking Humphries.

One is that more than one person in the organization believes he may end up being the Redskins' quarterback for the '90s. He's also more mobile than current backup Jeff Rutledge, and if something happens to Rypien, a quarterback with the ability to scramble may have a better chance of success against the Eagles' big pass rush.

Humphries started six games this season and his performances ran the gamut from terrific to awful. His debut against Phoenix in Week 4 couldn't have been better -- 20 of 25 for 257 yards and two touchdowns. But he struggled the next four weeks, throwing one touchdown pass and nine interceptions.

He was pulled Nov. 4 at Detroit, and Rutledge rallied the Redskins from 21 points down to a 41-38 overtime victory. Rutledge got the start the next week against Philadelphia, and both he and Humphries were hurt in that game. Rypien returned the next week -- Nov. 18 against New Orleans -- and has started every game since.