Disaster struck the $175,000 Washington Star International Tennis Championships yesterday. Not rain. Not thunder or lightning. Worse.

Missing one ground stroke after another, Jimmy Connors, the top seed and the only player in the field capable of selling tickets, was stunned by unknown Frenchman Pascal Portes, 6-4, 7-5, in front of 5,200 afternoon fans at the Rock Creek Tennis Stadium.

Connors did not lose to an upstart playing the match of his life. He lost because time and again, as he said later, "I didn't even get the ball into play."

It was the third match in 24 hours for both players. Portes, 21, ranked No. 128 on the ATP computer coming into the tournament, moved into the quarterfinals by waiting patiently for Connors to err. Then he came up with some solid tennis when Connors finnaly pulled up his electric-blue socks long enough to get into the match.

Before the Star tournament, Portes had played in 11 tournaments this year, winning only six matches.

"He didn't play very well," Portes said. "He missed all sorts of shots, especially on the forehand. I know he can play better."

Connors, outwardly calm in defeat except for a brief angry exchange with a local television reporter who asked questions he considered stupid, tried to give Portes credit. But he admitted, "I was out of control on a lot of balls. I had a lot of 15-40 games on my serve and I was never really able to get anything solid going."

On a perfect day for tennis, Connors was the only favorite player to have trouble. Third-seeded Gene Mayer didn't even have to take the court to reach the quarterfinals, winning by default when 14th-seeded Phil Dent withdrew because of a bad back.

Sixth-seeded Brian Gottfried had only a little more trouble than Mayer, romping to a 6-4, 6-2 win over Spain's Fernando Luna. Ninth-seeded Victor Pecci was even more dominant, advancing to a quarterfinal match with Mayer by beating 34-year-old Chilean Jaime Fillol, 6-2, 6-2. Fillol was playing his third match in 24 hours.

Thirteenth-seeded Corrado Barazzutti also moved into the quarterfinals, where he will play Portes, with a 6-3, 7-5 victor over Ecuador's Andres Gomez.

The evening matches were also quick two-setters.

First, Zeljko Franulovic, the stately 33-year-old Yugoslav who upset Harold Solomon Wednesday, blew Ramesh Krishnan off the court, 6-4, 6-0, never letting the young Indian into the match, keeping him pinned to the baseline. Franulovic plays Gottfried next.

Then Mel Purcell, darling of the crowd when he beat Eddie Dibbs Wednesday, was routed, 6-2, 6-2,

"He had me confused," Purcell said. "Last night, everything went right. Tonight, everything went wrong."

Several hours earlier, the same could be said for Connors.

Few in the stadium had heard of the Frenchman with the curly-brown shoulder-length hair before he trudged onto the court with Connors. Even the chair umpire spent the entire first set mispronouncing his last name -- it is pronounced Ports, not Portez. Finally, Portes corrected him. By that time, he was no stranger to the crowd.

The match had started innocently enough, both players holding serve the first five games, Portes leading, 3-2. Then, in the sixth game, Connors' ground game began to go awry. He missed two backhands -- Connors normally doesn't miss two backhands in a month -- to go down to 0-30. At 15-30, he missed a third backhand, then was wide on a drop shot attempt, giving Portes the game.

Portes couldn't stand the prosperity, missing an easy backhand to let Connors break right back to 3-4. The crowd, clearly behind Connors, was fidgety, but still calm.

Both men held to reach 4-5 on Connors' serve. Then Connors, No. 3 player in the world, began to lose it. Serving to even the set at 5-5, he played a horrid game.

First, he missed a backhand. Portes matched him, also missing one. Connor missed a forehand before Portes hit one of the few genuine winners of the set, a backhand down the line, to get 15-40.A moment later, he had the set as Connors netted an easy forehand.

"I played okay until 4-all the first set," Connors insisted. "He broke me, but I broke right back. Then I got a little careless, lost my concentration and let him get the set."

Still, Connors had dropped a set Wednesday night to George Hardie and come back to win. But in the second set, his play deteriorated further.

After surviving two break points in the first game, Portes broke Connors in the fourth game, nailing an overhead on break point.

Each man held serve until Portes served for the match at 5-3. By now, many in the crowd could hardly believe what was happening, with Connors' exit appearing imminent.

But, as he has done so many times in his career, Connors dug deep when he appeared beaten. Rather than stay back and rally with Portes, he became aggressive, coming to the net, in effect to saying to Portes, "You aren't going to pull this off without hitting some winners."

The tactic worked. The key game was the ninth, Portes serving for the match. Down, 30-0, Connors flashed the form that had made him the world's No. 1 player for six years.

He put away a short forehand, set up by a gorgeous drop shot. Then, at 30-15, he saved three straight overhead, finally got a net and knocked a backhand winner past a lunging Portes.

Shaken, Portes badly missed a backhand passing shot and Connors had break point. He missed a backhand. But he slammed another backhand winner past Portes and got the Frenchman to net a volley after just getting a hard first serve into play.

It was 4-5. Moments later, it was 5-5, Connors holding serve at 30. The crowd sensed that Portes was in trouble. So did Portes.

"I was very nervous," he said. "I didn't want to go into a third set. When you are up a set and 5-2 against the No. 3 player in the world and you have to go to a third set, it is hard to get your concentration back.

"I tried not to think about anything. If I had thought, I would have choked."

Connors didn't let hm choke. With Portes serving at 5-all, Connors quickly had a break point. But he missed an easy backhand, one that caused him to curse himself aloud.

"If I win that point, who knows what happened?" he said. "If he had gone from up 5-2 to down 5-6 with me, serving for the set, it would have been hard for him, I think. But it didn't happen."

Instead, Portes held for 6-5 when Connors missed another forehand. Portes led, 15-40, with two match points.

Connors survived one with a nice volley. But then, appropriately enough, he netted another backhand and the match was over.

The crowd was so stunned it almost forgot to applaud Portes, whose biggest win before yesterday was in Switzerland a year ago, over Guillermo Vilas. Finally, as he picked up his gear to leave the court, the audience came to its feet to salute his upset.

Much to the relief of tournament officials, Sunday's final is already sold out and will not be affected by Connor's defeat . . . The ATP media guide notes that Portes, 21, is the "protege" of Yannick Noah. Noah, the menter, is 20 . . .