Some days are diamonds; some days are better.

For the Redskins, yesterday was the first game under Joe Gibbs that the offense was potent enough for most fans, and perhaps more than a few players, to openly root for the opposition to score. There never was any danger of losing, and a Cardinal touchdown set the stage for another thrill from Mike Nelms.

Nelms comes as close as a bully gets to ballet. So tough and nimble was this reckless Redskin that you figured St. Louis should try an onsides kickoff after every touchdown. Why not? Nelms was going to run anything directed his way to midfield anyway. At least.

"When he gets it," said Joe Washington, "forget it."

Not quite. Unlike the week before, against the Patriots, and three weeks before that, against the 49ers, Nelms did not get to the end zone yesterday. He did get 84 yards on one kickoff, 40 yards on one punt return and 191 yards in all. With a record for the running long jump over a prone beast, Nelms was the star of a terrific NFL track meet.

The RFK Stadium customers have grown accustomed to Nelms treating his body as though it were a jackhammer, sticking it into walls of tacklers and somehow punching his way free. On that 84-yard kickoff return early in the fourth quarter, he tried to fly.

As he dashed up the middle of the field, Cardinals converged left and right. The one smack in front of him fell. So Nelms did what any insane man hell-bent on dying young would do. He hurdled him. Jumped right over a big bird believed to be Randy Love.

And survived.

Anyone who leaps in NFL traffic usually counts his limbs when he comes back down, so mean are the defensive missles who usually zero in on the helpless body. Minds get scrambled; backs get snapped; knees get bent in ugly angles. A man can leave the ground a star and return retired.

Nelms violated all the NFL rules of safety and survived untouched. Hurried on for another 50 yards or so, in fact. This was possible, Nelms insists, because he is not as crazy as we assume.

"Conservative recklessness is what I'd call it," he said. "When I leave my feet, I'm aware I'm off the ground, that I'm vulnerable. I look around before I jump. I expected to get hit (on that leap), from the left or right. I was prepared to take a lick.

"But it never came."

Surprised no Cardinal had even pecked him in mid-air, Nelms later stiff-armed a tackler and then slowed enough to be wrestled to earth at the St. Louis 12. The Redskins scored their fifth touchdown in three plays.

Most of us were startled not that Nelms ran so well but that the Cardinals let him. This is one of the premier game-breakers in the NFL, and the haughty Cardinals dared him to help beat them. Which he did. Intelligent men working 18-hour days should be bright enough to order the ball kicked in any direction but toward Nelms.

"They probably kicked off to him," said Wayne Sevier. special teams coach, "because they tried to kick away from (Eddie) Payton last week against the Vikings and kicked three out of bounds. You don't want to rekick over and over. Punts are different. Some subtleties are involved.

"What you want (other than to simply boot the ball out of bounds) is to punt so you can bottle the returner up against the sideline. We did that against Stump Mitchell. But to do that you have to change your punt protection. It might not sound like much, but it is.

"They may not have been willing to do that."

Nelms would have.

"I'd leave me alone," he said.

Let's allow some other very good kick returners to brag on Nelms.

"Never saw anyone like him for getting out of trouble," said Terry Metcalf. "Guys can be swarmin' all over him, relaxing almost because they figure they've got him. Next thing you know here's Nelms comin' out of the crowd.

"He's a spirit builder."

"Real strong," said Washington. "Anyone who tries to tackle him around the shoulders probably won't do it. And he knows he's good. They can kick away from him, but if it stays inbounds he's gonna get it."

"Strength is his real key," said Sevier. "Like the way he shook off (the Patriots Terry) Sanford last week. That and confidence. He can go into a pile, get hit four of five times and keep rocking. Nobody realizes how fast he is, because he's so smooth.

"Most returners take what they can get, go down and save themselves. And I'm not saying that's bad. Mike takes what he can get, and when he doesn't have anything he takes 'em head on, bounces off and still gets something anyway."

Yesterday was almost a complete flip-flop from the earlier game against the Cardinals in St. Louis. The quarterback we were calling a dunce back about then, Theismann, was brilliant yesterday. Hart was sensational in St. Louis; he was dreadful yesterday.

It was 14-0 yesterday before the Redskins experienced a third down. On the 80-yard drive for their third touchdown, the Redskins had just two third downs. That is efficiency.

With Nelms hampered by injuries, the Redskin special teams were about as bad as possible in St. Louis. With Nelms healthy, they were splendid here. There was some eerie irony: The Redskins' Jeff Bostic was hurt in St. Louis; The Cardinals' Joe Bostic, Jeff's brother, was hurt in Washington.

Among Washingtonians these days, the light debate is whether Nelms or interest rates are tougher to bring down. He is being appreciated more with each daring dash.

"I noticed the crowd (buzz as he goes back to field kicks) this time," he said. "It was like it used to be in Canada. I love it."