Two little-known clay court players disrupted what should have been routine quarterfinal matches for top-seeded John McEnroe and Ivan Lendl today in the Tournament of Champions tennis tournament at the West Side Tennis Club at Forest Hills.

Claudio Panatta already had his 6 p.m. flight back to Italy booked, but he fought listless McEnroe for 2 hours 42 minutes before McEnroe, the first seed, won, 3-6, 6-2, 7-6 (7-5), to advance to Saturday's semifinals.

Second-seeded Lendl experienced some uncomfortable moments against hard-hitting Lawson Duncan before winning, 6-3, 6-3.

In another quarterfinal, Henrik Sundstrom defeated Terry Moor, 6-1, 6-2, in 50 minutes, setting up a meeting with McEnroe (WJLA-TV-7, 3 p.m.). Third seeded Aaron Krickstein advanced to play Lendl by beating frequent practice partner Brad Gilbert, 6-3, 7-6. In a night match that had 11 service breaks, Krickstein fought from a 4-1 deficit in the second set and won the tie breaker, 7-5.

Panatta, 25, held off two match points against McEnroe before losing in the tie breaker. He had booked his flight to Rome Thursday when he realized he would be facing McEnroe.

"I was confident, but it was McEnroe, and you know you're going to lose," said Panatta, who qualified for this champions-only tournament by winning a $75,000 event in his hometown of Bari, Italy, in April. "The last couple of weeks, I've been playing well so I was sure it would be a good match, but not like this. When you go 7-6 in the third it's almost a win. The tie breaker is just a lottery."

McEnroe took a 3-0 lead in the tie breaker. Panatta fought back to 4-3, but McEnroe hit an unreturnable serve and a drop shot fell in for triple match point.

Panatta's forehand volley somehow climbed over the net to end one match point, and then McEnroe almost did himself in when he mis-hit another forehand. But at 6-5, on the third match point, McEnroe hit a vintage backhand volley cross court to make his escape.

McEnroe was virtually motionless in losing the first set as Panatta broke him in the fourth and sixth games. His usually flawless drop shots fell into the net. In the match, he had 50 unforced errors.

But McEnroe, the two-time defending champion, finally awoke in the second set with a series of line disputes and two service breaks. He won an 18-point game, holding serve despite five break points, to go up, 5-2, and then broke Panatta to force the third set.

"I felt lethargic in the first set," McEnroe said. "But I didn't feel as bad as I looked. Things just weren't going anywhere. I felt I was in the match in the second set, and I expected to win the third, 6-2. I sure didn't expect 7-6 in the third."

Lendl, looking more trim and agile than he has in some time, wore an old T-shirt after his match that said "No More Mr. Nice Guy." He needed a little meanness to get by Duncan.

"Those days are over," Lendl said of the shirt. "I'm going back to my old image."

Duncan, a surprise quarterfinalist from Asheville, N.C., is a rarity, a U.S. clay court specialist. He displayed strong backhands and seemingly inexhaustible patience from the base line on Forest Hills' clay. He also added a touch of swagger.

Duncan, 20, a Clemson star who was runner-up in last year's NCAA championships as a freshman, had said Thursday of Lendl, "I feel I'm better than him from the base line. I honestly do."

What he didn't have was a serve. Lendl broke serve when he had to, twice in each set, to end the match after 1 hour 25 minutes.

Duncan, however, had a couple of timely breaks to make the match more entertaining than the score would indicate. He broke back in the first set to even things at 2-2 after falling behind, 2-0. In the second set, he broke Lendl in the first game and held for a 2-0 lead.

But Lendl quickly put things back in order, winning four straight games. Duncan threatened once more, putting Lendl at a 0-40 deficit in the final game. But Lendl won the next five points, putting the match away with a forehand volley.

"He ran down too many of my points," Duncan said. "He moved really well. I hit some really hard shots, four of five of them would have been winners against anybody else. But he would get them back deep and start the point over."

Lendl, not renowned for speed, displayed new mobility in chasing Lawson's monstrous topspin ground strokes. A new diet and fitness program made Lendl appear more gaunt than usual.

"I've been working hard since the U.S. Open last year," he said. "It's just now showing up.

"He played awfully well. I was glad he didn't serve too hard. I felt I had to hustle for a lot of balls. He was pushing me."