Fenway Park is one of baseball's lovable dinosaurs, a playground where the paying customers sit close enough to tell their adored heroes what bums they really are. If you're the league's most valuable player, they'll make life a standing ovation. But they'll boo up a thunderstorm if you demand more money the next year. And if you then get hurt and can't play, life becomes a fast ball hight and tight.

Fred Lynn knows. A rookie with the Boston Red Sox in 1975, Lynn hit .331, won the MVP award and gained a spot in our memory by leaping against the concrete in Fenway's center field to catch a line drive in the World Series. By the calendar of, say, a plumber, 1975 wasn't long ago, but 40,000 customers haven't been booing his pipes daily. For Fred Lynn, 1975 is the good oldays.

When Lynn, shortstop Rick Burleson and catcher Carlton Fisk refused to sign new contracts in 1976 - finally agreeing in August - the Fenway faithful reminded the heroes of their mortality. They booed a lot. "It was," Lynn said today, "a new sensation."

To make things worse. Lynn played while injured. At five different times, he had muscle pulls and bruises that should have kept in bed, resting. But he played until mid-September when he sprained his right wrist in batting practice and couldn't swing a bat. The fans demonstrated their customary civility by booing Lynn while he watched his teammates work.

"It was one of those injuries you can't see." Lynn said. "I wasn't limping or anything, so they couldn't understand why I wasn't playing. I just couldn't hold on to the bat. Every time I swung, I lost the bat. It bothered me that people thought I could play and I was loafing."

While Lynn hit .310 in 1976, he had only 10 home runs and 65 runs batted in.

"After the end of last season, I thought I'd never have a season that tough again," Lynee said.

He's changed his mind.

Lynn is hitting ,257 this year.

And he's limping.

And he's been limping since March 24.

"This year has been so much tougher than last year," he said.

Vince Lombardi, who made the Green Bay Packers a great football team, said his athletes had to ignore the little hurts. Play with pain. Because most good athletes come equipped with a sense of immortality - their bodies are indestructible, they often go to work when a plumber, say, would be checking into a hospital.

On March 24, in spring training, Lynn ripped apart the tendons in his left ankle when his spikes caught in the dirt during a slide. He was in a cast a month and couldn't run for a month after that. So be missed about 25 games. "And the fans thought I was still loafing," Lynn said.

We should pause to say this: Lynn isn't angry at the Fenway folks. He smiles when he talks about the lovelies. It's just that he's young (25) and bright (a graduate of Southern California) and the whole thing has been a learning experience. What he wants, and is certain he'll get, is to hear those standing ovations again.

He once thought they'd never end, for in a world of imperfect people scratching to make it, Fred Lynn was one of those masterful creations who seem to glide through life. It was as if he didn't even try to be so good: it just happened.

During the 1975 World Series, Lynn was a star. So reporters surrounded him, asking him, in effect, how he did it. Tell us, Fred, how did you perfect a swing so smooth, so level, that line drives explode from the bat? Tell us, Fred, did you know you hads that line drive all the way? And where'd you learn to jump into the wall like that?

To all those questions, Lynn had no answers.

"I was a natural," Lynn said. "Everything came easy. I'd see the ball and hit it. That's all."

Suddenly, the game is more difficult for Lynn.

Because of the pain in his left ankle, he developed a series of bad habits at the plate this season. He'd come back to work too quickly ("I didn't want the fans on me any more"). And the pain ruined the smooth, level swing of 1975. He has 15 home runs and 62 runs batted in, which are respectable figures for imperfect creatures, but Lynn isn't happy with them.

"This thing has affected me," he said. "I never hit under.300 in my life and now I see that .250 and I say, 'Geez, what's going on here?'

"Until I got hurt, I was hitting about .440 in the spring. Really crushing the ball. I thought I was going to have a year like I did in '75.

"But I haven't been at 100 per cent once all season. About 90 per cent is the best I've been, and that was for a few games at a time."

Running on artificial turf hurts the ankle. Lynn twice has jumped against walls, hurting it. Walking up and down stairs hurts it. Until this year, he'd never taped an ankle for baseball. Now he wears a thick wrapping on the left ankle, distorting its shape under the sock.

"All of a sudden," Lynn said, "I appreciate more what I used to be."

Then he smiled.

"But I have no doubts I would have had a great year this year. And I will have great years in the future."