What the Redskins should do is give John Riggins another week at his hideout in Kansas.

Then, if the fugitive fullback still hasn't figured out right from wrong, the Redskins should trade him.

Give his job to Clarence Harmon, who can do it.

Then trade Riggins for another running back, or a defensive end, and a No. 1 draft choice.

Trade him, this is, if they can find any NFL general manager foolish enough to guarantee $800,000 for two years to a running back who, the evidence says, already is working on borrowed time.

Cold there, that line about "borrowed time."

Cold but true, and the NFL is a cold business. Riggins joked about it a week ago in phone calls to the Washington TV and newspaper guys, implying he was a 230-pound "beef future."

It is no joke. As much as the Redskin coaches and players like Riggins for the zest he brings to his work and game -- how many millionaire fullbacks come to practice on a motorcycle? -- they know the bottom line is that John Riggins, fullback, is a commodity to be bought and sold and traded.

And as a commodity, Riggins is flawed.

Flawed by age.

He is 31 years old.

This would be Riggins' 10th season in a game in which the average running back lasts four years. The best runner ever, O. J. Simpson, had eight good seasons before playing out the string with three bad ones. The odds are not on John Riggins' side.

He knows it. That's why he is sitting at home in Kansas, hoping his absence brings the Redskins management begging at his doorstep. This season is the last on a five-year contract at $300,000 a year that Riggins and George Allen worked out in 1976. That contract also had an option year, which means that at the Redskins' option they could retain Riggins' services for a sixth season at $330,000.

At age 26, Riggins must have liked the contract. He did sign it. It was worth $1.83 million. The deal must have looked good to Riggins at 26, with only five years of NFL battering behind him.

But now, as all running backs do in time, Riggins sees the end coming. He sees it coming from a blindside block, sees it coming from a linebacker exploding against his knee, sees it coming from a misstep that sends the Achilles' tendon rolling up like a windowshade. At 31, the immortality of age 26 is but a memory foolish in the recall.

So Riggins wants a guarantee. He wants the option year of his contract guaranteed. That is, he wants to be paid for that option year whether or not he plays. Allen guaranteed the first three years of Riggins' six-year deal. That way, the club and the player split the risk -- three years of guaranteed pay, three more years there for the earning.

A fair deal right? The Redskins had to pay Riggins $900,000 even if he broke a leg the first day in camp and never played again. To get that guarantee, Riggins agreed to three more years with the Redskins at his peril -- with $900,000 more to be earned by simply making the team.

He did more than make the roster. With 1,153 yards rushing last year, Riggins had the best year of his life. He was the ninth-leading groundgainer in the NFL. Three times he had 100-yard games, including 151 yards in the classic 35-34 loss to Dallas.

Though Riggins walked out of training camp before the 1979 season began, trying then to upgrade his contract, he returned meekly. He had no leverage then. This time he feels he has leverage, coming off his best year ever, a year that marked him a star. So he is in Kansas, likely waiting for the Redskins to capitulate on either the guarantee or the raise to $500,000.

He should not hold his breath.

The Redskins will not, and should not, change a word of the deal they struck five years ago.

Bobby Dandridge took a run at the Bullets in the same way. After agreeing to a three-year contract worth $250,000 a season, Dandridge led the Bullets to the NBA championship. So he decided he was worth more than that $250,000. He probably was. But a deal is a deal.Had Dandridge been a flop, the Bullets would not have demanded a refund on their money. It would have been their tough luck -- just as it was Dandridge's tough luck to become a more valuable player than he thought he was.

Dandridge and Riggins want it both ways. They want the security and big money of a long-term contract. But they also want to change the contract if they have a great year. As hard as I press my ear to the ground, I hear nothing from Kansas that suggests John Riggins wants to give back any of the $300,000 he was paid in each of his first two years with the Redskins -- years in which he gained a total of 775 yards, only six yards more than he gained in his single rookie season five years earlier.

It is a cold business.

The best pro sports franchises do not renegotiate fair contracts. If a Robert Brazile, an all-pro linebacker, is stuck with a $50,000-a-year contract he signed as an unknown kid, he is right to ask for a raise. It is an unfair deal on the face of it. For John Riggins, a $1.83 million fullback, the deal is fair.

If $1.83 million fullbacks can get away with forcing renegotiation, then soon enough general managers' offices will have to be supplied with those number gizmos butcher shops put on the counter. Take a number, Mr. Quarterback, we'll renegotiate with you next.

Renegotiation would be chaos. You take your best shot at contract-signing time. Riggins took his $1.83 million shot five years ago. He should live by his agreement.

It is a cold business.

At 31, time is against Riggins.

The Redskins are not about to guarantee $330,000, much less a half-million, to a running back who will be 32 when his 11th season begins.

Do you know how many of the 45 leading ground-gainers in the National Conference last season were 30 years old?

Two.

O. J. Simpson, giving farewell appearances on one leg, was 32.

To find another runner longer in the tooth than Riggins, you have to go to 46th place in the NFC rushing statistics. There you find Archie Manning, a quarterback three months Riggins' senior.