Washington Redskins starting wide receiver Calvin Muhammad, who did not catch a pass in Sunday's 19-6 upset loss to Philadelphia, has diabetes and admitted he was "drained" going into that game.

"I worked very hard on the weights last week and ran a lot of deep patterns in practice, so, come Sunday, I just didn't have it," Muhammad said after practice at Redskin Park yesterday.

"I was drained. I was tired physically. (The diabetes) added to it a little bit."

Muhammad, 26, has known for five years he has had diabetes, a condition involving an insulin deficiency and characterized by excess of sugar in the blood. However, his illness was not made public until yesterday, when Coach Joe Gibbs said it may have contributed to his performance last Sunday. Redskins owner Jack Kent Cooke said the illness was not a surprise to the team.

In the Philadelphia game, Muhammad dropped two passes, one of which might have gone for a touchdown. In one difficult stretch of the third quarter, Muhammad dropped the ball on a comeback pattern on first down; ran the wrong route, failing to go deep, on second down; and did not get both feet in bounds on Joe Theismann's slightly overthrown pass on third down.

Muhammad, acquired Oct. 3, 1984, in a trade with the Los Angeles Raiders, caught 42 passes for 729 yards in 10 games last season as a replacement for the injured Charlie Brown, who was traded to Atlanta last month. He had four games with more than 100 yards receiving last season.

This season, he has caught only six passes for 87 yards, but, perhaps more importantly, has been one of the reasons why the Redskins, losers of two of their first three games, have had a surprisingly inconsistent passing attack.

"He's having some trouble with really feeling strong and peppy," Gibbs said.

The Redskins asked Muhammad to undergo blood tests Tuesday to make sure he is receiving the right amount of insulin. Muhammad said he has not yet received the results of the tests.

"I think it may have something to do (with diabetes) . . . so we're double-checking from the medical standpoint and the insulin standpoint," Gibbs said.

Muhammad, who said he was "disappointed" with his play Sunday, said he also is not used to playing in hot, humid weather.

Although he grew up in Jacksonville, Fla., he said he got used to the dry weather after two years in California and "had problems" during the Redskins' training camp in Carlisle, Pa.

"It's something I'm not accustomed to," he said. "That's part of it, too, definitely. I'm having to start all over, getting used to it."

Gibbs plans to use Gary Clark (two receptions for 27 yards) more Sunday at Chicago so Muhammad can rest when necessary.

"We're going to have to keep him fresher than what we are until it gets a little cooler," Gibbs said. "Last year when he came here, it was cool weather already. Hot weather right now is a factor.

"We're leaving him in there and he's running several long patterns and he just runs his guts out, so I think we're creating a little problem there. It's something we've got to work with."

But Gibbs said he has not given up on Muhammad, who is one of the fastest members of the team.

"I'm still sold on Calvin," he said. "When you lose, almost everything everybody else says sounds smart. Most of the time, the way people would see it on the outside is: 'Let's change. Let's get this, let's jerk this guy, let's get the quarterback, let's get the coach.' Whatever."

But Gibbs is not totally adverse to change. It's just going to be subtle, that's all. Figuring he may be pushing his players too hard, he dropped 10 plays from practice yesterday, lessening the load from about 80 plays to about 70 during the two-hour workout.

"I may have been pushing, from about Dallas week, really pushing hard," he said. "Our meetings and practices were longer. We like hard practices and we'll always have hard practices."

But, Gibbs said, the number of plays in practice was "creeping up a little bit," so he decided to drop some from the routine.

"We're down to 45 players and it's been pretty hot . . . it's probably a small thing, but it's one little thing I'm going to change.

"We need to get that real sharp, aggressive crispness back."

An abundance of work for some players is a concern, but so is too little work for running backs John Riggins and George Rogers.

Riggins and Gibbs met to discuss the running back's playing time, although neither will discuss specifics of their conversation.

"I think it's exactly the way John said it, 'It's something we've got to work out,' " Gibbs said.

But there are indications that neither Riggins nor Rogers is entirely pleased with the shared duties.

Said Rogers: "Either way you do it, it isn't going to be the right answer."

Said Riggins: "There are a lot of ways of skinning a cat. I don't know if (sharing carries almost equally) is the way or not."

Said Gibbs: "I doubt seriously if both guys at any time are going to be totally happy."

Rogers, who has carried one fewer time than Riggins (39 rushes to 40) but has a better average (5.1 yards to 4.0), said he believes Riggins will "start playing more."

Why? Because of Rogers' fumbles (five in seven games, including preseason), he said. "I'm a little depressed," Rogers said. "Fumbling is just something that's happening. I don't know how to solve it."

For now, Gibbs plans to stick with the pattern of the past three games: Riggins will start, Rogers will relieve him early, and the "hot" back will play more.

"It's something where we don't have all the answers yet," Gibbs said.

Safety Greg Williams sat out some drills yesterday with a sore right ankle, injured in the loss to Philadelphia. Head trainer Bubba Tyer said Williams should be fine by Sunday.

Offensive tackle Mark May is out of Arlington Hospital and back at practice after undergoing tests for a stomach disorder. Tyer said May "felt better yesterday than he has all season."

Center Jeff Bostic, recovering from reconstructive surgery on his right knee last October, returned to practice yesterday. He is eligible to return Oct. 15 off injured reserve.