Jimmy Connors, beginning his retribution against Bjorn Borg, beat the top-seeded Swede, 6-4, 6-2, 6-2, yesterday and regained the U.S. Open tennis championship.

Connors, who lost the title to Guillermo Vilas last year, jumped in the air, his arms raised, walked to the net and affectionately rubbed Borg's head after the decisive victory.

The 26-year-old American's triumph spoiled the 22-year-old Borg's bid for the Grand Slam. He previously won the French and Wimbledon titles.

Borg, his right thumb bandaged to protect a swollen, infected blister, lost his racket twice while serving. It was reported Borg had played with the aid of pain-killers. He did not ask the trainer's assistance during the match.

A standing-room-only crowd of 19,537 capped the series of record-breaking attendance figures. Total paid attendance for the two-week event reached 275,300 - nearly 57,000 more than last year.

Borg double-faulted six times and got only 58 percent of his first serves in while Connors never double-faulted, made 80 percent of his first serves and never was broken.

Borg has a history of problems at the Open.

In 1976, Borg suffered a severe groin injury and received pain-killing injections from the quarterfinals until his loss to Connors in the final. Last year, Borg quit with shoulder pain in midmatch against Dick Stockton in the fourth round.

Borg's thumb began throbbing Saturday night following his semifinal match with Vitas Gerulaitis. Bort's thumb was red and swollen and he was so concerned he called the tournament physician, Dr. Irving Glick, at midnight.

Borg wrapped his thumb with ice at Glick's suggestion and the swelling went down considerably. But Borg was still in pain and could not grip his racket comfortably in the morning when Glick visited him.

"We tried various types of padding but he said it felt too cumbersome." Glick said, "I gave him some anti-inflammatory medication."

Two hours before the finals Glick also injected a pain-killing drug directly into Borg's thumb.

"Half of his thumb he doen't feel," said Lennart Bergelin, Borg's Swedish coach.

Borg went out to practice with his fiance, Mariana Simonescue, and hit normally, although he kept looking at his taped thumb. Suddenly, Borg's racket flew out of his hand on an easy forehand and he looked concerned as he walked over to retrieve it.

Glick, watching Borg practice, was asked whether the injury could affect Borg's play, especially in a long match.

"It surely could," Glick said. "He's hoping he'll get away with it. I used a strong pain killer but it will only last a few hours."

Connors, taking chances and attacking from the start, broke service in the fifth game. Games went with service the rest of the set.

Borg opened the second set with two aces both down the middle. He took the game at love, reaching 40-0 with an overhead cross-court and taking the game on a service winner.

But his serving success was spotty thereafter. Connors broke him in the third game, allowing him only one point. The fifth game went to deuce five times, Connors getting break point twice. The second time, Borg's racket flew from his hand as he served and landed near the net post.