Redskins coach George Allen opened a special tryout camp today - for cornerbacks.

It was Allen's first public acknowledgement that the team in making contingency plans in case Pat Fischer, a 17-year veteran, cannot return from a pinched back nerve to man the left corner.

As Fischer remained in traction at Sibley Hospital in Washington, Allen brought in two prospects today: free agent Cliff Brooks, a six-year NFL vet whom they did not sign, and Skip Sharp, a rookie from Kansas who was placed on waivers by the Philadelphia Eagles Tuesday.

Under league rules, the Redskins had to sign Sharp and add him to the roster before he could practice because he had been claimed on waivers. To make room for him within the 60-player limit, the Redskins placed free-agent cornerback Larry Willis on waivers.

Allen said he planned to bring at least two or three other corberbacks into camp, and at least one unnamed free agent will get a tryout Friday morning before the team heads for Miami and Saturday night's exhibition game against the Dolophins.

Publicly, Allen was still taking the positive approach on Fischer's status. "I talked to Pat today. He feels better. It is encouraging. I predict he will be back," the coach said. "If it's humanly possible, Pat will be back. I hope we'll have him back when we return from Miami."

Privately, however, several team sources are not so sure Fischer can recover from this injury and play again. They say they really won't know anything until Fischer is able to walk on the field and practice without pain.

None of the cornerback prospects who will be here are household names. But the Redskins have less depth at cornerback than at any other position. Gerard Williams, who has taken Fischer's spot thus far, was the only reserve cornerback on last season's 34-man roster.

With Fischer hurt and Willis (who had failed a previous Redskin stint) cut, the Redskins have only two reserve cornerbacks in camp: Sharp and David Thomas, a WFL refugee who was on the injured-reserve list last year.

"We'll bring in defensive backs every day and keep evaluating our football team," said Allen, "so that if we do have to make a move, we can make a decision without wasting any time."

Sharp, who team sources say was Allen's personal selection, could be a "sleeper," according to the coach.The 5-foot-11, 185-pounder was Philadelphia's first draft choice, in the fifth round. Allen saw Sharp in a rookie scrimmage against the Eagles and talked to Sharp and his father Wednesday night.

"Sometimes when a guy's failed somewhere else, he realizes what he missed out on and becomes more dedicated. He has the ability," Allen said.

"I went up there (to the Eagles' camp) with the wrong attitude," Sharp said after his first practice. "I wasn't mentally ready to play football. I was in good sharp, the wasn't the problem. I was just feeling a lot of pressure being their first pick.

"I really didn't know if I wanted to play or not. In college there wasn't the same kind of pressure. I had to play well, sure, but it just wasn't the same. When I got my head together, I could play in this league. It was my own fault . . . Oh, yeah, I want to play now. I just blew a good opportunity."

Although wide receiver Frank Grant (mild knee strain), running back James Sykes (strained thigh), receiver Danny Buggs (mild knee strain) and guard Terry Hermeling (strained thigh left a marathon 2 1/2-hour practice early, trainer Bubba Tyer said only punt returner Eddie Brown and running back Mike Thomas, both with leg injuries, would not be ready for Miaim . . . Thomas did not participate in the drills; instead he worked with conditioning coach Jim coach Jim Curzi following a pow-wow between Allen, Tyer and team phsician Stanford Lavine . . . The Pigskin Club of Washington and about 250 youths from the D.C. Recreation Department's Roving Leader Program were guests of the team today . . . None of the 12 players placed on waivers by the team Tuesday were claimed by the 4 p.m. deadline today . . . Harold McLinton, No. 1 middle linebacker, took part in prepractice receiver drills today, causing starter Jean Fugett to deadpan, "You got a new tight end in camp here, coach?" . . . The Dolphins said today that starting quarterback Bob Griese will play a quarter against Washington Saturday night . . . The Redskins, who defeated Cleveland in their exhibition opener Monday night, complained of the long practice on this hot, muggy afternoon. "Short week, long practices," replied Allen.