Although the major thrust of his grievance with the Redskins if moot, John Riggins and the NFL Players Association still are pursuing an arbitrator's decision that they hope could grant him $300,000 or more in damages from Washington.

It was also learned that, under league rules, the Redskins have "tolled," or suspended, Riggins' contract for a season, meaning he still has one year and an option year left on his original pact with the team. The suspension could affect how soon Riggins begins receiving $800,000 in deferred payments.

The NFLPA and Riggins, whose salary if $300,000 a year, had wanted the arbitrator to make a decision before the end of the season on whether the Redskins improperly prevented him from playing football this year by placing him on the league's "retired-left camp" list. If the arbitrator had ruled in Riggins' favor, Washington would have been forced to add Riggins to the active roster.

But a date for the arbitrator to begin hearing the case has not been set, and a final decision is not expected until sometime in the spring, at the earliest. Riggins' case was sent to binding arbitration when a player-management committee deadlocked on his grievance during a hearing midway through the season.

However, the NFLPA still wants a ruling from the arbitrator on the validity of the "left camp-retired" category, which it claims was not agreed to or negotiated by the union in its bargaining agreement with the league. Any player placed on that list is declared out for the remainder of the season and cannot play for any league team during that time. The player also is denied his contractual salary.

Riggins and the NFLPA also have asked the arbitrator for unspecified damages from the Redskins, claiming the team denied Riggins the right to pursue his occupation by putting him in the left-camp category.

"We didn't ask for a specific amount of money, but the damages don't necessarily have to be confined to a player's salary," said Dick Berthelsen, NFLPA counsel. "By not being allowed to play this season, John probably has lost money far beyond his salary, in terms of his bargaining power for future contracts, endorsements, things like that.

"The arbitrator certainly has the power to grant a money award in this case. Although neither John nor the players association filed the original grievance for the major purpose of obtaining damages, there really isn't any other remedy left for John. The Redskins can't be forced to take him back for a season that is already over."

The "left-camp" category expires at the end of each year, but the Redskins would have the right to place Riggins back on the list before next season. Riggins, who left training camp in July and announced his retirement, has talked about coming back but says he has not made up his mind.

Larry Lucchino, the Redskin lawyer, said award of damages to Riggins, if he wins the arbitration, "would be nonsense. He did not want to play this season.He left camp voluntarily. He never did want to play. How can he be paid for something he didn't want to do?

"We are completely opposed to the idea of damages in this case. We never denied him anything. He made all the decisions on his own. We didn't tell him to go home to Lawrence, Kan."

The club and Riggins also could be headed for possible problems concerning the deferred money the Redskins owe him. Now that Washington has suspended his contract for a season, it doesn't expire until Feb. 1, 1983, instead of Feb. 1, 1982. Under terms of his contract, the Redskins are required to begin sending him annual $100,000 payments a month after the contract ends.

Team sources say Riggins is concerned that Washington will try to delay payments even longer, but Lucchino said the club "has no intention of being unreasonable about the deferred money. First, we have to see what John wants to do next season. If he decides to stay retired, we can sit down and work out a payment schedule."

If Riggins wants to resume playing, the Redskins can activate him, trade him (although he has trade approval rights) or waive him. His salary is not guaranteed, one of the things he wanted changed when he left camp.

General Manager Bobby Beathard has not ruled out taking back Riggins next season. However, a final decision on the fullback's status probably will rest with owner Jack Kent Cooke, who opted not to negotiate last summer with Riggins.