A 6-1, 6-1 loss to Frenchman Fabrice Santoro left Sampras dazed.

"I'm pretty stunned," Sampras said. "It's not great for the confidence. I mean, it's definitely not great for the confidence," Sampras said. "There is still a lot of room for improvement. All I can try to do is move on and learn from this and go from there."

It was his worst loss since a 6-0, 6-1 defeat in 1990 to Jonas Svensson of Sweden.

About the only positive thing about the defeat is that Sampras still has a chance to return to the top spot in the tennis rankings.

Marcelo Rios, who took over from Sampras last month, has an injured elbow and is not playing at this tournament, meaning the Chilean will forfeit the top spot.

However, Petr Korda, ranked No 3, could leapfrog No 2 Sampras and No 1 Rios to the top if he makes it to the title match. The Czech beat No 14 seed Albert Costa 5-7, 6-4, 6-4 inanother third-round match. Korda, the second seed, wasted a 5-0 lead in the first set.

If Korda loses before the final, Sampras returns to the top spot.

"At this point, sure, it would be nice to get back up there. But I know, and deep down that it comes down to the end of the year," Sampras said, who has ranked No 1 at the end of the last five years.

But if Sampras continues to play like he has over the last three tournaments, No 1 at the end of the year is far away.

It was the third consecutive tournament Sampras has lost before the quarter-finals and does not bode well for next month's French Open on clay courts. Santoro now faces compatriot Cedric Pioline next.

Pioline, who lost to Sampras in last year's Wimbledon final, topped last year's French Open winner, Gustavo Kuerten, 7-6 (8-6), 6-1. Boris Becker rushed past Marc Philippoussis, 6-1, 6-1 in 48 minutes to move into the quarter-finals against Alberto Berasategui, a 3-6, 6-3, 6-3 winner over Slava Dosedel. It is Becker's first quarter-finalsince Wimbledon when he said he was retiring from Grand Slam play and started only part-time on the circuit.

In other third-round matches, Richard Krajicek, the 1996 Wimbledon champion, topped Bohdan Ulihrach, 6-4, 6-0 and Carlos Moya upset Yevgeny Kafelnikov, the French Open winner two years ago, 6-2, 6-3.

Sixth-seeded Alex Corretja, last year's finalist, beat Andrea Gaudenzi, 7-6 (7-1), 6-4.

Chang struggles

LAKE BUENA VISTA: Defending champion Michael Chang overcame stubborn Franco Squillari 7-6 (7-2), 6-4 last night to advance to the quarter-finals of the US men's clay court championships.

The top-seeded Chang had to battle for nearly two hours to subdue the 22-year-old Squillari, who overcame an early service break to force the first set tie-breaker, then fought off six match points before sending a forehand wide on the seventh.

"I've lost matches before where I've had match points," Chang said, "So I never feel like it's over until I've actually closed it out."

For the secondstraight match, Chang's composure during a key tie-breaker was the difference in a tight match against a lesser-ranked opponent.

On Tuesday, Chang was pushed to the limit by Paraguay's Ramon Delgado, ranked 104th, before Delgado fell apart in the third set tie-breaker, allowing Chang to escape 6-4, 3-6, 7-6 (7-1).

Squillari, who entered this event ranked 101st by the ATP computer, was playing evenly with Chang until the first-set tie-breaker. But the Argentinean left-hander quickly fell behind 6-1, losing five points on unforced errors and eventually losing the tie-breaker 7-2.