It is an especially bitter frustration that a gifted athlete such as Lemar Parrish endures when his mind tells him to do something but his body can't.

It is a frustration that deepens when a receiver such as Philadelphia's Charles Smith, hardly an all-pro candidate, runs a routine pass pattern and gets open by five yards in the end zone for a touchdown, as he did against Parrish this season.

It is a frustration that increases when people begin wondering aloud if you've finally slowed a step, and you can't prove them wrong, although you are convinced you are as skillfull as ever.

"I've never been through anything like this," Parrish said yesterday. "It's been very, very difficult. I know I still can play, the coaches know it, my teammates know it. I just need to show it."

The season is 6 weeks old and Parrish doesn't have an interception. But he's been shut out for long stretches before, so he can handle that predicament.

What is different are the injuries. First a hamstring pull in training camp, then a right knee that had to be drained. The knee still hurts and now he is having to cope with a severe cold that has limited his practicing this week.

At 33, Parrish is the oldest Redskin, a 12-year professional who has played in the Pro Bowl eight times. Has age made him more vulnerable to injury, while whittling away at the extra quickness that separated him from most cornerbacks?

"No!" Parrish said, emphatically.

"No," said Defensive Coordinator Richie Petitbon, who made the controversial decision last year to bench Ken Houston and replace him with the younger Tony Peters because Petitbon was convinced Houston had become too old.

"I may not be as quick as I was 10 years ago," Parrish said, "but I've made up for that with experience. I may be 33 but I think I'm 21.

"If I'm healthy, I can play to the same level I always have. But this has been terrible. I've had to be conservative, I've had to hang back and not take chances. That's not the way I want to play. I want to make things happen, I want to make the big plays. That's my role on this team and I haven't been fulfilling it."

Parrish said he became so frustrated with being in and out of the lineup this season that he talked with Coach Joe Gibbs. Did Gibbs think Parrish was hurting the team? Did he want to make changes?

"Coach told me to stay with it, that I'd be okay," Parrish said between coughs. "He said things would be okay as soon as I healed up. I can't ever remember fighting things this hard. I've been hurt before, but this time my legs were affected. I need my legs."

There are two styles of playing cornerback in the National Football League. One is the physical way; its foremost proponent is Lester Hayes, a bump-and-run specialist even in this era of restrictive rules for defenders. The other way relies on technique and quickness; Parrish long has been considered the league's finest practitioner of this method. But only if his legs are sound.

"When Lemar is right, he's still one of the best, no question about it," Petitbon said. "He can go man to man with the best of them. I'm sure age has hurt him some, but I don't see that he's different from other years. He just hasn't been healthy. He's been hurt since the middle of training camp and hasn't practiced a full week since then. Even someone as good as Lemar needs to do more work than that. Otherwise, your sharpness is affected."

A healthy Parrish is necessary to the Redskins' complicated defensive scheme, which generates a pass rush by blitzing. But when a blitz is called, the defensive backs are left in man-to-man coverage. And without Parrish at full speed, that isn't as effective. So Petitbon is forced to gamble less and opposing quarterbacks have more time to pass.

Likewise, Washington's nickel defense is far weaker when Parrish is hobbling. And if the nickel can't stop third-and-long plays, everything else usually breaks down quickly.

Some of that old joy returned for Parrish last week in Chicago. He got his hands on four passes and tormented the Bears' receivers with characteristically tight coverage. And it was no coincidence that the Redskin secondary had its best game this season.

"If it wasn't for this cold, I'd be the best I've been since training camp," Parrish said. "I'm still not there yet. If I was, I would have had one or two interceptions last week. Anytime I touch the ball four times, I should pick off two, at least.

"I still want to play. And I still want those interceptions. Nothing in football feels better than an interception. You burn to get one. I really want one bad, because I know turnovers will help us."

Parrish laughed. "The oldest Redskin, huh? I remember when I was a rookie and 22. I looked around and saw those old guys in the locker room and couldn't believe how old they looked. Now I'm one of those old guys. But don't count this old man out. He still can play."