what the Redskins need now, Billy Kilmer has. They need grace under pressure. After a wonderful five or six games, Joe Theismann came down with a bad case of the panics Sunday. Before this thing becomes an epidemic, the Redskins ought to try to proven cure: Billy Kilmer at quarterback.

For the moment, anyway, Theismann has played himself out of the job, just as, in the preseason and in the early games, he so spectacularly earned it. Never had Theismann been better longer. He had promised a transformation. He would be a disciplined quarterback. Instead of trying the hero's work - going deep for the bomb, or scrambling about - Theismann would be patient and let the system be the hero.

And he did it. When he retreated into the end zone before President Carter's eyes with the ball held overhead in a silly salute, Theismann had quarterbacked the Redskins to a 9-5 victory over the Dallas Cowboys. "Sure, he's good," an old-time Redskin had said of Theismann last summer, "but can he score against Dallas inside the 20?"

In the euphoria produced by the victory over the Cowboys, it was overlooked that, in fact, Theismann did not score from inside the 20. All he managed were three field goals. But no one much cared, for Theismann had been masterful, sustaining a strong offense against the best defense in the NFL last year.

Theismann won the Detroit game a week later with a touchdown pass in the last two minutes. But only that late score made his performance commendable, and mediocre performances the last two weeks in losses to Philadelphia and New York produced the inevitable Joe-or-Billy arguments.

It is time for Kilmer.

Not because the Redskins, with Theismann, have lost two in a row.

But because Theismann last Sunday was so gawdawful when it mattered most.

Theismann admitted his failing, but the confession did not produce any more points and served best to remind listeners that George Allen, the famous sports columnist, recently waxed poetic over Kilmer's courage and leadership. For an important fourth-quarter, drive, Allen said, Kilmer is the man he wants. In Allen's opus, rating quarterbacks on everything from hat to cleats, Theismann did not draw a mention.

For those who believe Theismann, at 29, is ready to be a star in the NFL (it was after the Dallas game that I thought I sighted Theismann on the rise, Staubach descending), the quarterback's work Sunday against the Giants was disheartening.

He panicked. He threw into double coverage. Some of his passes would have been out of reach for Kareem Abdul Jabbar. Under pressure, he showed no patience. As evidence, there is this; Theismann, in the late going, threw nothing but fast balls.

He needed a changeup. At all ranges, from 10 yards to 30 yards, Theismann threw the ball as hard as he could. It bounced off people. When Jean Fugett's vise-grip hands can't hold a pass, it is thrown too hard. The worst of it is that in earlier games Theismann had shown a nice touch with a soft pass. But with a game on the line, he lost that touch and tried to throw the ball through defenders - hurrying thepasses into quickly closing gaps - Instead of over them.

That is a mistake coaches will not tolerate. It is a mistake Billy Kilmer would not make. It is not in Kilmer to be heroic, to make happen by the power of his being. He isn't pretty and doesn't care. He can't out-run your Aunt Harriet and doesn't care. As $220,000-a-year relief pitchers go, he doesn't have much of a fast ball. No Goose Gossage he.

But when the clock is running down and you are losing a football game, Kilmer can win it back. Don't ask how. The guy is 39 years old and his hair is gray and his face is red. Because he has earned the name, old-timers call him "Whisky." All of which means nothing late in a game. Then this old man is beautiful.

No one should expect Kilmer to be Theismann.The "new" Redskins' offense may suddenly resemble the familiar snore-maker of Allen. Kilmer simply can't throw the ball hard enough or far enough to go with pass patterns Theismann has used.

At game's end, though, Kilmer's passes - perhaps wobbly, perhaps' short - will be caught by his own guys.