Testimony in Washington Redskin fullback John Riggins' long-delayed grievance against the team will begin today in Washington before arbitrator Bert Luskin.

Riggins, who walked out of training camp last summer in a contract dispute and did not play last season, reported to last week's Redskin mini-camp and said he wants to play in 1981.

He contends the Redskins acted illegally when they placed him in a "left camp-retired" category five days after he left camp. That action made Riggins, the team's leading ground gainer with 1,153 yards rushing in 1979, ineligible for play anywhere in the NFL, a move he says was tantamount to depriving him of the means to earn his livelihood.

The Redskins have said there was no impropriety in their actions.

Hearings are scheduled today and Friday, but a decision on the matter is not expected before midsummer.

Riggins left camp last summer after the club refused to meet his demands that the option year of his contract be changed to a one-year, $500,000 guaranteed contract.

Through the National Football League Players Association, he filed a grievance in September challenging the Redskins' right to deny him the opportunity of playing.

In the grievance he said he had notified the club by telegram during the five-day period that he was retired voluntarily. He said he later changed his mind and wanted to play during the 1980 season but could not because of the way the Redskins had classified him.

If a player retires voluntarily, he is eligible for reinstatement by the commissioner.

"Riggins' telegram made it absolutely clear that he desired to continue playing while under contract to the Redskins," said Ed Garvey, executive director of the NFLPA. "To treat Riggins in a fashion different from any other retired player would be arbitrary and capricious.

"Players in the NFL are tired of the clubs' continued refusal to live within the letter and spirit of the collective bargaining agreement, and of their refusal to bargain in good faith with veteran players. The Riggins case is one more example that control is more important to the club than winning," Garvey said.

At issue in the arbitration, in addition to the specifics of the Riggins case, is expected to be the propriety of the left camp-retired category, Garvey said.

The case will come to arbitration after a four-member panel, consisting of two representatives of the players, deadlocked, 2-2, on the matter.

Should Riggins lose the arbitration, he would have one year left on his contract, at $300,000 a year, plus the option year, the same situation that existed when he left camp last July.

A finding in Riggins' favor could bring him $300,000 in lost compensation for sitting out the season and a ruling that he is now entering the option year of his contract.