Midway through the second quarter of Sunday's National Football League Players Association all-star game, Washington's John Riggins discovered the benefit of trying to stay in shape during the NFL strike.

Not much.

"I was huffing and puffing pretty good out there," Riggins said, before heading for Los Angeles to play in the Monday night NFLPA game, too. "I had been doing some running and I thought I was in pretty good shape. I was wrong."

If this strike ends in time to continue the 1982 season, Riggins will have plenty of huffers and puffers for company.

Even players who have trained diligently since the walkout haven't been able to prevent a gradual conditioning deterioration that likely has dropped them to mid-training camp shape.

"No matter how hard the players have tried to stay in shape, it's not the same as having a coach standing there pushing them," said Dallas Coach Tom Landry. "I think most will come back in good shape but it will take up to three weeks to get them back to top form again."

During those three weeks, NFL coaches and players interviewed recently believe:

* Players will be much more susceptible to injuries, especially the small, nagging kind that occur early in training camp. In the summer, there is time for those ailments to heal. Athletes won't have that same luxury after the strike.

"If you aren't in top shape, you aren't always able to react to a given situation the way you usually would," said Baltimore Coach Frank Kush. "Your mind sees the cut or the tackle or the block, but your body can't keep up. That opens the way to getting hurt."

* Veteran teams could have a decided advantage in the early weeks.

"So much of the game is mental," said Redskin Coach Joe Gibbs, "and the veterans who have been around four or five years have heard the stuff (plays) so much, it's easy for them to pick it up again. The young guy won't feel as comfortable. He just was getting to where he thought he had things down, and now he has to start over again."

* There will be even more emphasis on passing, especially in the initial poststrike games.

"The receivers and quarterbacks have had the easiest time staying sharp because it's easier to get people together to play throw and catch," Landry said. "It will take linemen longer to come along, making it harder to run. So there should be more passing, even more than there was already."

* Those players who have viewed the strike as a long-term vacation away from physical activity have made a significant mistake.

"If they come back out of shape, they are gone for the rest of the year," said Kansas City Coach Marv Levy. "There just won't be enough time to help those people out. I'm sure all the coaches are anxious to see who applied themselves and who dropped off. It will tell a lot about their work habits."

Gibbs: "If a guy is a player and he doesn't come back in decent shape, I'll see it. Those people eventually won't be around. You don't want players who can't motivate themselves enough."

* Those teams that have continued organized workouts of some sort during the strike will have a major advantage.

"Those teams won't be starting from scratch," said Gibbs, whose quarterbacks, receivers and backs have been holding group workouts two or three times a week lately. "As a coach, you have to hope they've tried to keep some sort of team approach. Timing is so important in the passing game. You just can't walk away from that for a few weeks and then expect to pick up that quickly."

AFC coaches admit they already are concerned about the Miami Dolphins and the San Diego Chargers. Players from both teams have been conducting full-scale workouts since the strike started, with attendance reaching the high 30s for most practices. In the NFC, the Philadelphia Eagles have had no formal practices the last 28 days.

"Those early days after the strike ends are going to be brutal," said the Jets' Wesley Walker. "Your body has gotten away from the punishment of contact and all that forced running. People are going to be dragging around. This is such a physical sport. It takes time to get used to that again."

Miami's Ed Newman: "No matter how much running you have done, you can't be in hitting shape. You have to put on pads again and get whacked around for a while. Linemen use training camp to get used to contact. There is a reason behind spending four weeks beating up on each other."

Kush, the master of contact, says players may have more difficulty accepting the mental aspect of contact work than the actual hitting.

"Contact is painful but you have to get it ingrained in your mind to go after someone," Kush said. "It's not a natural thing to do. That's why so much repetition is necessary. Players are going to have to accept the fact that they will be sore for a while once they come back."

Lack of time, of course, will be a major obstacle, both to the players and to the coaches.

"You can get refreshed mentally pretty fast in practices," said Washington linebacker Mel Kaufman. "But you can't get enough full-speed work to get back into shape right away. That's going to show up the first game or two."

Minnesota's Bud Grant figures teams with more quality players will have an edge, since they will be able to compensate better for player fatigue problems. Grant also has a hunch that some teams will make lineup changes at first, going with players who have a quicker recall.

Ideally, the coaches say they would like two or three days to concentrate on conditioning -- "a full week would be best," said Levy, who would then like another week to prepare for the first poststrike game. Realistically, most hope for at least six days before the opener, although Miami's Don Shula says he would feel comfortable if the Dolphins practiced just four days.

"We are not going to have any special conditioning program when they (the Redskins) come back," Gibbs said. "I don't think we will have time to go back and do special things to get them in shape. My first concern is to win our first game. To do that, I think we have to follow a normal game week practice schedule. I may keep them out a little longer, but there won't be that much change in our normal approach."

Kush, however, is considering two-a-day workouts for his young Colts, at least at first, so he can give his players a quick refresher course.

"We have so much to relearn," he said. "We are so young that nothing will seem that familiar. I would use the morning workout to go over everything again, just like it was training camp. The afternoon would be a regular practice. I intend to test them in ten 40s (sprints) when they come back. If they are at 70 percent of the best condition, we'll be okay. If they are less, we are in trouble."

Landry: "You have to be careful not to push too hard. If you do, you will have a dead-legged team by Sunday. What you want is a team that will play well in spurts. That's the best you can expect, and you can't have spurts if you are worn down."

Gibbs: "No matter what, the players won't be as smooth and as polished. We see it all the time with players who come off injured reserve. They aren't as confident and they are thinking more than reacting."

Levy believes the best approach will be to keep it simple.

However, everyone admits to only guessing what will happen once the strike ends. There hasn't been another regular season NFL strike to use as reference, although Gibbs remembers what happened once the preseason 1974 walkout was over.

"I was in St. Louis and the players came back on a Wednesday," he said. "Don Coryell was the head coach and we had a game that Saturday. He decided that the regulars would play no matter what. I thought it would be awful, but it wasn't. Instead, it went very smooth. It was almost as if they hadn't been away at all. Surprised me a lot."