In what he had called "absolutely, for sure" the biggest match of his life, Bjorn Borg reached back yesterday and produced absolutely, for sure the finest tennis seen at Wimbledon this year, and perhaps in many years.

The 22-year-old Swede turned what everyone expected to be a gripping duel into a startling execution, gunning down arch-rival Jimmy Connors, 6-2, 6-2, 6-3, to capture the most cherished prize in tennis for the third consecutive year.

Borg is the first man to win three successive Wimbledon singles titles since Englishman Fred Perry in 1934-35-36, and now has the first two legs of the traditional French-Wimbledon-U.S.-Australian Gran Slam achieved by only two men; Don Budge (1938) and Rod Laver (1962 and '69).

Borg, in devastating form, was the aggressor throughout the match, swarming the net on grass as successfully as he attacks from the back court on clay.

He served ferociously, especially on the most critical points, and followed every first serve to the net.

He cleverly varied his usual barrage of heavily topspun ground strokes, frequently slicing backhand approach shots short and low to Connors' vulnerable forehand, coming in behind them for telling volleys.

He pinned Connors, who served poorly, to the baseline, ripping his returns hard and deep, punishing Connors's short second serves.

"I was not scared of his game when he was serving," said Borg, who lost his serve only once, to trail 0-2 in the first set, and then ran off six games in a row, climbing on top to stay, "I felt I could maybe break even every single time."

It was murder in the cathedral of tennis, and at the finish Borg dropped to his knees in a prayerful pose and looked heavenward, toward the gloomy, leaden skies that had smiled on him.

On the last point, Borg hit one of his shortest returns of the 1 hour 49 minute match, a forehead off a Connors first serve. The brash left-hander from Belleville, Ill., who chose to stay back on his first serve most of the afternoon, came steaming in behind a deep forehand approach shot. Borg drilled a backhand down-the-line passing shot. Connors lunged for it and punched a backhand volley long to lose his serve for the seventh and last time.

As the ball whistled beyond the baseline. Borg dropped his racket, sliped to his knees, clasped his hands together and raised them above his head, as if to say "Amen" and "Thanks."

Still kneeling on the turf, he turned to the competitors' guest box, elevated in one corner of the Elizabethan-style Centre Court stadium at the All England Lawn Tennis and Croquet Club. There his fiancee, Rumanian player Mariana Simionescu, and his coach, Swedish Davis Cup captain Lennart Bergelin, were beaming, sharing the jubilation of his proudest moment.

Perry, still dapper and robust at 69, rushed from his microphone in the BBC radio booth to Centre Court a few moments later. He hugged Borg, and offered condolences to Connors, who seemed not to hear.

"He just congratulated me, and then said I had to shave," Borg said. This was a prior gentlemen's agreement. Borg had promised Perry that if he equaled his feat, he would put a razor to the scruffy whiskers he has tried for three years, without success, to cultivate into a respectable beard.

Borg received $34,200, but he had said repeatedly that money means nothing here, at the game's shrine. What is priceless is the golden trophy he received from the Duke and Duchess of Kent in Wimbledon's brief, dignified, moving presentation ceremonies, then held aloft for photographers and the gallery before returning it to a circular table draped with a Union Jack.

There have been five more decisive men's finals at Wimbledon in the postwar era, but none so surprising, between players of such similarly high standard. The only performance comparable to Borg's ironically, was Connors' 6-1, 6-1, 6-4 ravaging of Ken Rosewall in 1974, the first of his four finals and only championship here.

Rosewall, in his fourth final at age 40, was the sentimental favorite that year, but he was eaten alive by Connors, Pancho Segura, Connors' coach called his 20-year-old charge "a lion, a ruthless killer who could dominate this place for a decade."

That final did not have the sense of occasion yesterday's did, given Borg's dream of matching Perry's 42-year-old "hat trick" and the grandeur of past Borg-Connors encounters.

Theirs has been the men's tennis rivalry of the '70s, characterized by bruising, uncompromising matches played full-throttle from first ball to last. The Wimbledon final a year ago was once of those, Borg winning by 3-6, 6-2, 6-1, 5-7, 6-4, after Connors surged from 0-4 to 4-4 in the final set.

Connors still leads the series, 8-6, but Borg has won three of four meetings in 1978, five of the last six over two years.

Borg routed Connors, 6-1, 6-2, in Tokyo in April in a four-man exhibition tournament that received little attention outside Japan. "That was one of my best matches ever," Borg said. But it wasn't until he flattened "Jimbo" again yesterday - with 14,000 spectators watching live and millions more on global television - that the world appreciated just what that meant.

Four weeks ago, Borg pummeled Guillermo Vilas, the second-best player in the world on slow clay courts, 6-1, 6-1, 6-3, in the final of the French Open, the premier clay court test. He begrudged Connors, the second-best player on fast grass, only two more games in the oldest and most important tournament of all.

Borg is the first player since Rod Laver in 1962 to sweep the Italian, French, and Wimbledon titles in one summer. And after rising so splendidly to his most challenging moment, there can be no lingering doubt that he belongs in the company of the game's immortals.

"He's won three French, two Italian and three Wimbledon championships, that it not bad for a beginning, at 22," Perry said. "I didn't win my first Wimbledon until I was 25."

"This wasn't a great emotional final, in the sense of being close, but it was a demonstration of tennis you'd have to wait a lot of years to see again.

"Jimmy wasn't able to force him today. His serve wasn't working and he was struggling all the way. His two-handed (backhand) passing shot wasn't passing anything, and he made very few winners off it," Perry added.

"But Borg went for everything. He came in on every three-quarter-length ball, which he's never done before. The way he was playing, I think if he had fallen out of a 45-story window, he'd have gone straight up."

Borg did not play up to his 1976-77 form in the first week of this damp, dreary Wimbledon fortnight, which had only one day without rain. He was down two sets to one, 1-3 and 30-40 on his serve to victor Amaya in the first round and survived only by the margin of a gutsy second serve at that point.

But he played better with each passing round, and he showed a couple of new punches against Connors.

On big points, his once-suspect first serve is now as oppressive as anyone's. He has seldom, if ever, volleyed as surely. And the underspin backhand that paved his way to the net so often was a tactic for this special occasion.

"This was the first time I did that in a match," Borg said. "Usually that is not my game, but I found out that the court is pretty soft and the bounce very low because it has been raining so much. So if I could slice and come in to his forehead, I know he doesn't like that so much. I won so many points that way."

He won so many more by serving and volleying that Connors must have thought he was playing one of the Australian net-rushers who dominated Wimbledon in the 1960s, rather than the most consistent ground stroker in the game.

Borg walloped his usual allotment of topspin passing shots, especially backhand cross-court buzzers that dived into the court like Sandy Koufax curve balls, but it was his serve-volley attack that gave Connors no quarter.

"That was one of my plans, to come in more," Borg said. "Usually . . . he always puts pressure on me. I have to do the passing shot or the good lob. But today I realized I must put the pressure on him.

"I also had very good depth on my returns. Maybe Jimmy should have come in more on his serve, but it is difficult when you are missing so many first serves. Most of the time I kept him on the baseline, and I think maybe that's the way you have to play Jimmy.

"If you hit too many short ones, then immediately he's making an approach and coming in. I knew this before the match, if I don't keep him away from the net, then I'm going to be in a big trouble . . . But I had so much confidence in my serve and my ground strokes. I felt I could do anything."