Defensive back Charles Jackson, an ex-replacement player who was waived from the Washington Redskins' injured-reserve list Tuesday, filed a grievance with the NFL Players Association yesterday.

Jackson claims he still is bothered by a calf injury and should not have been released. The Redskins, meanwhile, issued a statement saying: "Charles Jackson's calf is still injured with atrophy in the muscle . . . However, {Jackson's} calf muscle has atrophied because, in the opinion of the Washington Redskins, he has not cooperated in proper rehabilitation."

Jackson, who attended Texas Tech, says: "Hey, they wanted me to do more than I was capable. It {the calf} just didn't respond as fast as they wanted."

The irony is that Jackson, who crossed the NFL players picket line, has now gone to the players association for help. And, what's more, the players association is backing him.

"Even though he's a replacement player, he's a player," said Clark Gaines of the NFLPA. "And we'll treat him the same as any dues-paying player."

Knowing what he knows now, Jackson says he probably wouldn't have crossed the picket line.

"If it weren't for the players association, I wouldn't know where to turn," he said. "Now, I can really see their side of it; why they were out on the picket line."

Jackson, who started at strong safety in the first replacement game against St. Louis on Oct. 4, was injured in the third quarter of that game. Trainer Bubba Tyer diagnosed it as a contusion strain of the calf muscle and figured Jackson would be out four to six weeks. When the strike ended, Jackson says the team offered to advance him two weeks pay if he'd go home. He said no, that his injury would take more than two weeks to heal.

At that point, Jackson says Bobby Beathard, the Redskins' general manager, accused him of "milking" the injury. To prove Beathard wrong, he says he went to an independent physician, a Dr. Thomas M. Walker, who told him it was a 10- to 12-week injury.

Jackson says he later got into a shouting match with Tyer, and he says the Redskins refused to let him keep his replacement game jersey or give him tickets to home games.

Beathard was unavailable for comment, and others in the Redskins front office refused comment.