With Bjorn Borg spending this year vacationing, pouting and protesting, the great queston in tennis was: which of the sport's young stars will profit most by Borg's absence -- John McEnroe or Ivan Lendl?

The answer has turned out to be: Jimmy Connors.

With McEnroe fighting the flame of fame, with Lendl still playing better for money than for glory, it has been Connors who has suddenly remerged as a bona fide claimant to tennis' uneasy throne.

With this summer's Wimbledon crown to his name, Connors may now be just one day away from winning the U.S. Open as well- the same sweep of the sport's two top prizes that he accomplished once before, in 1974.

Connors, who turned 30 a fortnight ago, had one of his finest hours today as he controlled Guillermo Vilas in a semifinal match, 6-1, 3-6, 6-2, 6-3.

Except for a brief second-set shift in strategy by Vilas, to which Connors quickly adjusted, there seemed Little doubt that Connors was headed to Sunday's 4 p.m. final (WDVM-TV-9). There, he will try to win his fourth Open title to go with victories in 1974, '76 and '78.

Opposing Connors will be the opponent of his choice: Lendl. This evening, Lendl erased McEnroe, 6-4, 6-4, 7-6 (8-6), to complete a dismal season for Super Brat. In one year, McEnroe has gone from child-emperor of tennis to a poor third in the sport behind Sunday's finalists.

In typical form, McEnroe, in Lendl's words, was "throwing rackets and screaming at umpires." McEnroe was also distracted by a cameraman wandering on court in the tie breaker. McEnroe called it "a very classless act . . . really disgraceful."

After his reign as '79-80-81 Open champ ended, McEnroe said he was very disappointed that his hometown crowd "boos me and is a always dumping on me . . . At least I'm young enough to regroup."

Lendl looked marvelous in performing the execution, returning Mack the Knife's slicing serves with elan and hitting passing shots just beyond the reach of McEnroe's rapid volleys. "The return of serve -- both ways -- is the reason I play better against him than I once did," said Lendl.

In a particularly pithy analysis, McEnroe had a simpler reason: "Lendl hits the ball harder than I do."

Despite Lendl's prime form, Connors said before the Lendl-McEnroe match that he would prefer to face the 22-year-old Czech, who is the tournament's No. 3 seed, but who has never won a Grand Slam event and has a history of shaky nerves under pressure.

Children play a schoolyard game in which rock breaks scissors, scissors cuts paper and paper covers rock. Tennis has an analogous, yet bizarre, situation. Borg beats Connors (10 in a row), Connors beats Lendl (eight of nine in their careers), Lendl beats McEnroe (six in a row now), yet McEnroe beats Borg in the megamatches ('80 and '81 U.S. Opens and '81 Wimbledon).

In this weird upper-echelon progression, Lendl is just the man Connors wants to see. Connors devours Lendl's serve. Connors stays at the base line, negating Lendl's passing shots. And Connors serves just well enough to keep Lendl at the base line where their concussive ground strokes are roughly equal: Connors' two-fisted backhand countered by Lendl's statuesque forehand. Connors has the biggest heart in tennis. Lendl doesn't.

Only one factor weighs against this. Connors and Lendl met two weeks ago in Cincinnati on an identical surface and Lendl won, 6-1, 6-1. "And I played a helluva game to keep it from being 6-1, 6-1," said Connors.

Despite that match, this whole tennis year has had a Connors' stamp, much, for instance, as '81 seemed to fall in McEnroe's lap.

"I wanted to win Wimbledon one more time. And I did. Now, I want to win the Open one more time, too," said Connors. "This is my tournament. The fans are for me. They're nuts and I'm nuts. We get along fine . . . There was a time they didn't like me here, I'll guarantee you that . . . Maybe now they feel sorry for an old man running around out there."

For Connors to get back to No. 1 in the world would be one of sport's fairy tale events. "I've always enjoyed it from up there," said Connors, speaking of the top ranking he held continuously from July 1974 until April 1979 and which he has coveted every day since he lost it.

This afternoon, the veteranbase- liner Vilas, who has battled Connors on even terms for years (their lifetime record is now 5-5) got a dose of the old, but improved Connors. The 150-pounder still had his old grunting fury from the base line, but he also had a harder and more consistent first serve (77 percent this day), as well as a midmatch flexibility in strategy that completely closed out Vilas' chances.

"He played very risky shots," said Vilas. "He went for the lines and for difficult angles. So, he deserves it. If they hadn't gone in . . . I would win in four sets. Not many can do that."

Vilas resorted to top spin from both wings in the second set and perplexed Connors. "His top spin was jumping at me high and hard. It took a while to figure out how to handle it. You can't go for a winner right off the bat. Wait for a short ball, then go for the winner."

Then, the old man got out of his chair and his eyes got large. He grabbed both thighs and began torub vigorously. Next, he began to jog in a simian crouch while still rubbing.

"Leg cramps . . . bad," said Connors as he jogged toward the trainer's room, bent like an old man.

An old man of 30 who just wants one more healthy day.