For the last three years, Jose-Luis Clerc has played brilliant but often unnoticed tennis in the foreboding shadow of his Argentine countryman, Guillermo Vilas. Last night, before a capacity crowd at Rock Creek Tennis Stadium, Clerc stepped to form an identity all his own by winning the Washington Star International with 7-5, 6-2 victory over Vilas.

Clerc, 22 the fifth-ranked player in the world, pounced on Vilas from the opening point. Clerc served well, played steadily from the base line and volleyed crisply the few times he found it necessary to come to net.

Vilas, who won this championship in 1975, 1977 and 1979, had not lost a match in the Star International since the 1974 final to Harold Solomon. But Vilas never reached his championship-winning form last night.

His serve was inept -- just a weak tap to start the point -- and he looked very out of place at net. Most surprising was the huge number of unforced errors Vilas committed on base line ground strokes -- his forte in the past.

But many of Vilas' mistakes were a function of Clerc's exceptionally strong game. With the posssible exceptionally strong game. With the possible exception of Bjorn Borg, Clerc may be the best clay court player in the world.

Clerc has all the ingredients to dominate matches on clay -- the hard kicking serve, consistent ground strokes, lobs, spins and patience -- and the probably the best physical condition of any player in the game.

"He has everything he needs to become the best player in the world," Vilas said afterward.

Clerc's championship victory last night -- one year after a final-round loss to Brian Gottfried -- may move Clerc past Ivan Lendl into the No. 4 spot in the ATP computer rankings.

It must be noted, however, that neither finalist met a seeded opponent en route to the championship match. Both benefited greatly from a rash of upsets in the early rounds. And neither played inspired, world-beating tennis in the first set.

Clerc beat Vilas for only the second time in nine matches, and picked up the $28,000 first prize. Runner-up Vilas collected $14,000, but he maintained his hero status in the eyes of several hundred fans from Argentina who made the trip north to see this match.

While Vilas talked with a mob of reporters, the Argentines chanted his name so loudly outside a nearby fence that Vilas' always soft voice was barely audible. Tournament officials chose a new path for Vilas to walk to the locker room to avoid a wild aftermath. Clerc's greeting, although loud and gracious, was not nearly as overwhelming.

Perhaps the spectators, like Clerc, still were stunned by the relative ease of the victory. "I'm really surprised I beat him in two sets," Clerc said. "I'm playing very well on clay courts. When I went onto the court, I felt especially good tonight."

Clerc won the first game easily, on a winner and three unforced errors by Vilas. But Vilas held serve for a 1-1 tie on four unforced errors by Clerc.

Clerc held for a 2-1 lead on three more unforced errors and a winner to Vilas's backhand. Vilas managed to hold service, but Clerc was starting to reduce his errors.

Clerc took a 3-2 lead with an ace on the final point, broke Vilas, then held serve again for 5-2.

"Then I sort of lost concentration," said Clerc. Clerc had one set point, but committed two unforced errors and handed Vilas a break on a double fault. In one of the best-played games of the match, Vilas scored a stunning drop shot and two passing shots to tie the set, 5-5.

But Vilas' serve would tell on him again. Trailing, 6-5, after Clerc had held serve, Vilas lost the set game at love on four sissy serves.

"My serve was never the best part of my game," Vilas said. "If anything goes wrong with my game, I would expect it to be my serve."

But this serve should have been an embarrassment to Vilas. The ball floated over the net like a Luis Tiant-type offering. It just didn't have enough juice to keep a player of Clerc's talent from stepping up to take a whack at a return.

"Vilas never hit the ball hard on his first serve," Clerc would say later.

Clerc, on the other side, was serving as deep as possible to the backhand, with plenty of kick and velocity. He wrecked Vilas with six aces and at least four more service winners. Vilas scored no aces and never used his serve as a weapon, part of the reason he played most of the match on the defensive.

"It was so important that I got those aces," Clerc said, "especially against Vilas because he returns serve so well."

Vilas didn't do anything especially well in the second set. Clerc broke serve in the second game of the set and held twice to take a 3-0 lead.

At this point, Clerc had eliminated the mistakes that had forced a close first set. By the time Clerc took a 5-1 lead in the second, he had toasted Vilas with 10 winners, seven of them blasts from the base line.

"His play from the base line was very consistent," Vilas conceded afterward. "I had a chance in the first set, but I didn't play consistently enough. I shouldn't have let him take control of the match from the beginning."

As Vilas pointed out, since the Italian Open Clerc has played exceptional tennis. He has won 33 of 36 matches since May and two straight tournaments. "The biggest difference between his play now and his past performances is that his ground strokes from the base line have improved," Vilas said.

It was rare indeed for Vilas, who once won 57 straight matches on clay with untouchable ground strokes, to be outdueled from the base line.

But then, Clerc had so much riding on this match, although he wouldn't admit it.Even though he had defeated Vilas in a five-set final last year at Madrid, Clerc had defaulted in their last meeting, at Barcelona, with Vilas leading, 4-0.

"For me," Clerc said, "the rankings in Argentina are not important. I don't know which of us is No. 1 there at the moment. Only the world rankings are important."

Raul Ramirez and Van Winitsky, trailing, 2-5, in the third set after fighting off two match points against them in a second-set tie breaker, won the Star doubles championship, 5-7, 7-6, 7-6, over Ferdi Taygan and Pavel Slozil.

The final featured some pulsating points in the course of more than three hours of play (breakfast at the Star), including two tie breakers, which Raminez and Winitsky won, 9-7 and 8-6. Slozil and Taygan fought off two match points in the third set.