Sometime soon, running back Joe Washington's unharnessed optimism might run right into the harsh reality of the Washington Redskins' numbers game.

Washington, who has been on injured reserve since spraining his left knee at New England in the fourth game of the season, wants to play. The coaches want him to play. But, in one of the ironies of the Redskins' injury-strewn season, he may not be able to.

Washington, who wears a metal knee brace when he runs, says he feels good and "could play this week" at Philadelphia. But he won't. The coaches want to wait longer, and even Washington admits he is not going to be reactivated to play on artificial turf, his nemesis.

For now, the reason Washington isn't back is simple. He still has swelling in his knee, and, as of 10 days ago, his injured knee had only 82 percent of the strength of his good knee.

Washington says he is back to "92.5 percent, maybe even more." It shouldn't be long before he adds the final 7.5. But even when he gets healthy, he still might not be brought back.

The Redskins may reactivate three more players from the injured-reserve list during the regular season, plus one more in the postseason. They likely will bring all-pro free safety Mark Murphy back in move No. 1 later this week. That leaves two moves in a regular season that still holds five games. And that means trouble.

Coach Joe Gibbs was talking about the problem yesterday after practice at Redskin Park.

"If Joe is 90 percent, we use a move and he goes in there, all it takes is one tweak on that AstroTurf again and he's out of there and we've wasted the move," Gibbs said.

"If the guys are really producing in the spots where we have somebody, then you've got to say to yourself, 'If we're getting great production out of the backfield with the guys that are there, how much more is Joe going to help us?' That's what you have to say."

With John Riggins practicing more than he has in weeks and Keith Griffin just off a 114-yard day against Detroit, the prospects at running back look good. Gibbs is the first to admit it, saying he is "very pleased" with the play of the back-ups at the position.

Gibbs said he will wait to "the last second" on any move he makes, whether it is Murphy, Washington, wide receiver Charlie Brown (ankle) or whomever.

"It just may come down to it that we can't activate those guys," Gibbs said. "I would make those moves right away, if we had that luxury."

So the only game Washington will play for the time being is the one in which you spend most of your time carrying your helmet, not a football. It's called the waiting game.

"I think I'm well enough to play this week," he said yesterday, "but I don't think they will activate me. They wouldn't want me coming back on artificial turf."

But Washington figures they might want him back for the Buffalo game the following week at RFK Stadium.

"I feel real good, but as much time as I can buy, the better off I can be down the stretch," he said. "It's tough to wait, but I get bored when I'm fine, too. I'm a positive person. I don't want any sob story. I don't want to see anything like, 'Old poor Joe, he's hurt.' Everything's positive."

Injuries continued to rule the theme of Gibbs' postpractice meetings with reporters, but everything seemed positive there, too. Center Rick Donnalley, who suffered a mild sprain of the medial collateral ligament in his left knee during practice Tuesday, walked through drills yesterday and is expected to play as usual against Philadelphia.

"I felt a lot better than I expected," Donnalley said after practice. "I played pretty much pain-free. I'm pretty sure I can play."

Gibbs said he "anticipates" Donnalley and left guard Russ Grimm, who has a slightly separated shoulder, will "be okay and ready to go." Grimm also spent most of his time walking through drills.

Cornerback Darrell Green was kicked accidentally in practice by defensive end Charles Mann and has a bruised shin, but is expected to practice and play. "He's okay," trainer Bubba Tyer said.

Injuries are nothing new to Washington, an eight-year veteran from Oklahoma who missed all of his rookie year with a knee injury and has become well acquainted with arthroscopic knee surgery over the years.

It's this medical history that makes Gibbs even more concerned.

"Joe will come to me when he's ready," Gibbs said. "I think he's still a ways off. We really have to be careful with him. He has to be a no-doubter. Because of his past history, he's really going to have to feel great, he's going to have to be 100 percent. He'll have to be roaring.

"I want to wait until I'm sure, I'm positive."

Don Breaux, the running backs coach, spends some time each day practicing handoffs with Riggins and Washington. He says Washington is running at three-quarter speed and just needs a little more time.

"He must be feeling pretty good because I hear him humming around the complex," Breaux said.

But Washington says he always hums.

"I want to keep them on their toes, to see if they could appear on 'Name That Tune,' " Washington said.

He presents a happy exterior. But, inside, Washington realizes that playing might require more than being healthy again.

"I think," he said, "we have enough people that can do all the things I do."