The Washington Redskins' defensive secondary was set more in sand than in stone last season, as injuries and uneven performances contributed to a state of flux for many of the 16 weeks.

That situation will persist at least through the early stages of training camp with the absence of cornerback A.J. Johnson. His status as a starter was not etched in granite, but now that he is likely out for the season with a bad knee, more uncertainty looms.

Darrell Green, who dislocated his wrist in October, is healthy again, but the other corner position could belong to Brian Davis or Wayne Davis or Martin Mayhew or . . .

"It doesn't matter who would start now," said assistant head coach for defense Richie Petitbon. "It's who starts against Phoenix {in the season opener, Sept. 9}. One of them will emerge."

Johnson's hopes for playing in the 1990 season are all but gone after he had major knee surgery Monday.

"Being realistic, I'm not sure that we'll get him back this year," Petitbon said. "It will take some time. As I understand it, he came out of it real well. I suppose there's always a possibility that at the end of the season -- the playoffs, maybe -- that he could come back. That would be a tremendous boost, but that's being very optimistic."

Johnson could not be reached for comment. A receiver and defensive back in his senior year at Southwest Texas State, he was picked in the sixth round of the 1989 draft. He made a solid first impression at last year's minicamp, then had people watching in the heat and humidity of training camp.

"Once the season started, he developed a knee problem," Petitbon said. "But he didn't tell us and he sagged. When he got a chance to play, it was kind of a coincidence that his knee got better. He did a real fine job."

Johnson played in all 16 games, and was a starter for the last eight. He finished the year with 47 tackles and in a tie for the team lead in interceptions (four) with Brian Davis and Alvin Walton. His best game was in early December, when he intercepted two passes in the Redskins' 29-10 win in Phoenix.

But the knee trouble did not go away. Early last month, Johnson had arthroscopic surgery and it was discovered that the anterior cruciate ligament was damaged enough to require major surgery.

Brian Davis started nine of the 15 games in which he played, while registering 59 tackles and the four interceptions. Wayne Davis, who played in eight games after signing Nov. 1, had eight tackles and one interception. Mayhew played in every game, started the last seven and finished with 47 tackles and no interceptions. The Redskins also list D'Juan Francisco, their 10th-round draft choice from Notre Dame, at cornerback.