The Washington Redskins, rulers of the National Football League last season, will open their castle door Thursday to begin their training camp in Carlisle, Pa. Once the door is opened, they must prepare to raise their shields.

That's because even before the challenges of fall come the questions of summer; they come especially when you win the Super Bowl.

Coach Joe Gibbs keeps talking about enthusiasm and total team effort and that perhaps Green Bay of the '60s didn't need those things to dominate, but that the Redskins of the '80s do.

"Those are the kind of things we have to get back. We aren't the kind of team that can physically wear other teams down," Gibbs said.

The players see it this way: "We should go into camp arrogant, not cocky just to be bragging, but arrogant in the sense that we are proud that we have a job to do and now we know we can do it," said Mark May, the offensive guard who is among the veterans scheduled to report July 24. Only rookies and selected veterans will report on Thursday.

"No matter what anybody says, when you win a Super Bowl, you get conceited," said Russ Grimm, another offensive guard. "But I think this camp might even be tougher than last year's camp. You don't want to change things just because you're winning."

There are a number of key questions facing the defending Super Bowl champions as they prepare to take 100 players to their 21st camp at Dickinson College, where practices come twice a day and pleasures of self-indulgence come none a day:

Cornerback Jeris White, 30, is unsigned. Team officials fear that White, with direction from agent Howard Slusher, might duplicate his 1981 holdout, when he did not report until just before the regular season.

That situation, and the off-season retirement of 10-year cornerback Joe Lavender, mean the left cornerback job (opposite Vernon Dean) and the pressure might fall on Darrell Green, the first-round draft pick from Texas A&I.

Redskins officials like Green's speed (he ran a team-best 4.3 in the 40-yard dash at minicamp), but they also have fears about his size. They worry that a fullback like the New York Giants' Rob Carpenter will make a 5-foot-8, 170-pound cornerback seem like a mere bug on the windshield.

"Back in 1981 when Jeris held out, things were different," said Tony Peters, the Redskins' starting strong safety. "We had Joe Lavender and Lemar Parrish, two all-pro veterans. Jeris was basically just a fill-in . . . Now, we don't have experience at the corners.

"Vernon Dean played very well last year, but still he is only a second-year player now. The others (defensive backs), like Ken Coffey or Greg Williams, are good, but they are young, too. It's cause for concern, but it's not something to panic about."

With the departure to the U.S. Football League of offensive guard Fred Dean, who started in the Super Bowl, there is some doubt as to the new makeup of the offensive line.

Joe Bugel, the offensive line coach, who called Dean "a potential starter" before his departure, said he might move May from right guard to George Starke's right tackle position. Bugel also said he will consider Don Laster (second year, 6-foot-2, 300-pounder) and rookies Bob Winckler (drafted in the sixth round from Wisconsin) and Nathan Newton (free agent from Florida A&M) for the right guard spot.

In other words, Bugel isn't exactly sure what will happen. "With Freddie leaving, you lose a little depth," said Bugel, who termed Dean "a cog and a Hog."

"Now, you have to rely on a young kid coming in and being able to play in a critical situation without losing a heartbeat."

There is also concern about the recoveries of running back Joe Washington, who had operations on both knees last year and was reduced to 48 carries last season, and to wide receiver Art Monk, who broke a bone in his right foot in the regular-season finale against St. Louis and missed the postseason. Both players are considered crucial to the offense.

Monk, 25, wore a cast for six weeks. "Because it was a broken bone, there was nothing I could do to strengthen it in the offseason, only resting," Monk said recently.

"I worked back gradually, doing some slow jogging and a little sprinting. I haven't done any agility tests yet, but I will partake in all of the exercises once we get to camp. Once the season starts, I'll be ready to go."

Washington, voted the Redskins' most valuable player in 1981 by his teammates, had operations on both knees over a three-week span in February. Redskins coaches stress Washington's importance as a receiver coming from out of the backfield, especially on third-down situations. They also stress his importance in keeping running back John Riggins from being overworked.

Washington, 29, continues to work out, lifting weights and running, and he talks confidently of carrying the ball 15 to 20 times per game this year. Team officials say the key to his recovery is more than just rebuilding his knees; he must rebuild his confidence.

Can Riggins, who will turn 34 before the season opener, maintain his peak level from last season? San Francisco Coach Bill Walsh insists that, beyond keeping injuries to a minimum, the key to winning a Super Bowl is receiving career-high performances from certain skill position players.

In last year's Redskins' 12-1 Super Bowl championship drive, Riggins gained 553 yards during the nine regular-season games last year, then 610 yards more in the four postseason games. In 1979, Riggins rushed for 1,153 yards in a 16-game season, but last year marked, without question, the apex of his career.

At the Redskins minicamp in May, Riggins said he felt no unusual pains or twinges in the offseason, despite 136 carries in the four playoff games, including 38 for 166 yards in the Super Bowl.

"I've felt worse after games when I carried the ball only 20 times than in games when I carry the ball 30-something times," Riggins said. "Blocking will take more out of your body than running the ball and being tackled."

Citing the importance of a completely recovered Joe Washington, Grimm said, "You won't see the Redskins come out and run John Riggins up the gut 30 times a game, 16 games a year. He's 34 years old. It's impossible. People just can't expect John Riggins to run like he did in last year's playoffs over the course of 16 games this year. But they can expect it in spurts."

The schedule, by virtue of the National Football League's competitive balance ("parity") system, is difficult. There are three Monday night games (home against Dallas, at San Diego and at Green Bay) and three West Coast trips (San Diego, Los Angeles Rams and Seattle). The season opener is Monday night, Sept. 5 against Dallas at RFK.

"All those Monday night games, all those time changes on the West Coast trips," said Gibbs. "The schedule is tough."

"That's absolutely perfect, opening up against Dallas," said Dexter Manley, the defensive end, showing a year has not altered his emotions one ember's worth. "Because the Cowboys just happen to be one of the teams I do not like."