Mark May, the Redskins' struggling 1981 first-round draft choice, returned to what his coach termed "training camp" yesterday in an attempt to salvage what has become a nightmarish season for him.

"We're starting from scratch, we're taking it like it is the first day of camp," Joe Bugel, the team's offensive line coach, said. "We're going to work on everything from his stance on up. He's got tremendous ability, but right now he needs to rethink everything."

It has been a week since May lost his starting left tackle job to another rookie, free agent Joe Jacoby. After an initial period in which he struggled to cope with the shock of his demotion, May says he is receptive to Bugel's instructions. And Bugel remains convinced May has a bright future in the league, despite this season's setback.

"I sat down and analyzed the whole situation, how a No. 1 could lose his job to a free agent," Bugel said. "I was one of the people who pushed hard to draft Mark No. 1, so I wanted to see if I had made a mistake.

"I'd admit it if I did, but I don't think we were wrong. If we had to do it again, I would suggest we take him when we did. He can play and he's going to have a long career. But he needed something to shake him up and get him to face reality."

Interviews with both Bugel and May reveal a portrait of a highly touted rookie trying to succeed in the National Football League without proper commitments either to weight training or on-field techniques.

May admits that he began to back off from mid-week weight lifting and that he let his body weight drop to 255 pounds after playing at 280 his senior year at Pittsburgh. And he said that as the season wore on, he would get more frustrated during games and try to handle opponents "by trying to kill them instead of using techniques. And it didn't work."

"Why did I stop lifting as much as I was? I don't really know," May said. "I just slacked off and they told me about it. In college, I really didn't lift that much and I was still okay. But there, you could beat people on pure muscle. Here, everyone is strong and you have to keep up your strength, you can't let them get an advantage on you.

"I know that now. If I had to do it over again, I'd come into camp weighing 280, bench-pressing 500 pounds and running a 4.7 40. Instead, I weighed maybe 263, lifted 375 and couldn't break 5.0 in the 40. But you learn."

Bugel says he regards May "as a 21-year-old pup who was the Outland Trophy winner, an all-America, a success at everything he's done, who came in here with a lot of pressure being the No. 1 choice and maybe he should have done things differently.

"Now he knows he has to do certain things to stay around. If he doesn't, he won't. They all have found out that no matter who you are, if you don't make a commitment, you are gone.

"He got too small and he let his strength go down. He'd lift and go home. You have to sweep (Russ) Grimm and Jacoby out of the weight room, they stay in there so long. Now Mark has to get himself built up, he needs to put on muscle and get up to 280. We've put him on a new program and he told me he's going to do it. That's what's encouraging. We had a father-and-son talk and he assured me he understands what happened and that he wants to be a success.

"We both knew he would get adverse publicity and that people would think he was a flop. It's something you have to live with. It's not the end of his career, but I have to think it taught him a lesson."

It was a lesson May would rather have avoided learning. He said he spent a lot of hours last week "sitting by a fire, thinking of what was happening, trying to handle it like a man. People would call and I didn't want to talk to them. Joe Bugel called it 'my sulking period' and maybe it was.

"Nothing like that had ever happened to me before. It took time for it to sink in. I knew I was hurt and I knew I was losing weight but I thought I could overcome it. I couldn't. You can't lose 1 1/2 inches off your arms and an inch off your neck during the season and stay the same. It doesn't work that way.

"It was a matter of choice for me. I could get down and stay down about what happened or I could look at it positively as the best thing that could happen to me. I can relax now and remind myself that this is my profession and to succeed, I have to do the right things.

"You can't glide here, it just doesn't work. It's a different world. Everything always had worked out for me, I was a starter, an all-America, a first-round pick. I got carried away. It was all sugar, and now I'm getting some salt thrown at me. I consider myself a fighter and I'll bounce back."

But what position he bounces back to remains a question. Jacoby, who is much stronger and bigger than May, could become a fixture at left tackle. Bugel says veteran George Starke, the right tackle, "can play another two or three years."

"I'm going to try Mark at guard next summer and at tackle," Bugel said. "I want him to be able to play both spots. Jacoby took to guard, maybe Mark would, too. Or maybe he's going to do it at tackle.

"But I told him he's going to succeed somewhere. We are in this together and he accepted it with open arms. That's an important first step for both of us."

Jacoby practiced briefly yesterday after X-rays of his sore right arm were negative. The Redskins expect him to start Sunday against the Detroit Lions . . . Rookie Mel Kaufman will continue to start at linebacker for Brad Dusek, who still is recovering from an assortment of injuries.