Four of the top seven seeds, including No. 6 Lindsay Davenport, notched straight-set victories in scorching heat to advance to the fourth round at Roland Garros, but Hewitt squandered a two sets to none lead and a break in the third set and fell to No. 28 Tommy Robredo of Spain, 4-6, 1-6, 6-3, 6-2, 6-3.
Hewitt continued his travails on clay. The reigning Wimbledon champion has not won a tournament on this surface since the 1999 Delray Beach event - his only title on clay.
The crucial moment in the final set came when Robredo broke the Australian to go up, 4-3, and he then held his own serve before breaking Hewitt again to take the match.
"If I could have kept going in the third set and played the way I did in the first two then I'm sure I would have been able to beat Tommy," said Hewitt, who had reached at least the fourth round here the previous three years.
"I never thought I had it in the bag because I wasn't holding my service games easy enough to even think about that but I had chances. I just didn't take them."
The tenacious 22-year-old endured his first loss after winning the first two sets.
"It's disappointing at the moment," he said. "I think I'll look back on it and I won't be that disappointed. Any loss in any tournament hurts straightaway, there's no doubt about it, particularly in a Grand Slam."
The 2000 junior finalist, Robredo matched his best result in a Grand Slam with Saturday's win.
"Lleyton is a guy who always gets another ball in. You have to play aggressive," he said. "I'm confident and that's why I beat him, because I tried all the time. I think I did a very good job with my mind and finally I could beat him."
The 21-year-old Catalonian's next opponent will be a clay-court specialist as he awaits the winner of Argentinian Gaston Gaudio's clash with three-time champion Gustavo Kuerten of Brazil. That match was halted due to rain with Kuerten leading 7-6 (7-1), 7-5, 3-3.
Hewitt's girlfriend, Clijsters, had an easy time advancing to the fourth round. The second seed from Belgium routed Argentina's Paola Suarez, 6-2, 6-1 and has lost just nine games this week.
"I've started playing really well. I was losing my concentration in earlier matches but today I was focused," said Clijsters.
Capriati also has dropped just nine games through the first three rounds. The seventh-seeded American steamrolled her way to a 6-1, 6-2 triumph against Julia Vakulenko, a 19-year-old Ukrainian playing her first Grand Slam.
The match lasted just 57 minutes, after which Capriati admitted her relaxed demeanor at the tournament she won in 2001 is due to her new philosophy on life.
"I'm trying to get my priorities in line," said the 27-year-old, who put her rebel youth behind her to win three Grand Slams in the past two years. "My philosophy is to be happy with yourself and comfortable in your own skin. There's life after tennis. I've had some personal stuff and now I don't let things bother me as much. It's just a waste of energy."
Along with Davenport, Capriati is now one of the "older" American women on the circuit but there is no thought of retirement.
"I still feel I can hang with the young guns in there. Inside me, I am still a youngster even though it seems another lifetime ago when I played my first Grand Slam," said Capriati, who reached the semifinal in her first Grand Slam here back in 1990 as a 14-year-old.
Williams bounced back from a tough outing to demolish Italy's Silvia Farina Elia, 6-1, 6-2. After struggling in her previous match against Austrian Evie Dominikovic and still troubled by an abdominal injury, the third-seeded American wrapped up the first set in just 23 minutes.
"I had better rhythm today and was serving better," said Williams, who has lost to her sister Serena in the final of the last four Grand Slams. "I feel I can do well. If I just get out there and fight I'll be OK."
Davenport battled through to the last 16 with a 6-3, 7-5 victory against Frenchwoman Nathalie Dechy, during which she suffered a flare-up of a nerve problem in the fourth toe of her left foot.
The American received treatment for the problem which has been bothering her for a month.
"The nerve gets very irritated," Davenport said. "But it's day-to-day, sometimes it's there, sometimes it's not. I'm just hoping it will be better tomorrow."
Davenport admitted that she holds no realistic hopes of eclipsing the likes of the Williams sisters and Clijsters to win the tournament, where she reached the semifinal in 1998.
"I consider myself an outsider," she said. "The other girls move better and hit the ball better. But I'll just do the best I can. It is not my best surface and I am just glad to be in the round of 16."
The Spaniard again showed his fighting spirit in the fourth set when he dropped his serve but broke back in the seventh and eighth games then held his nerve in a tense final game to take the set and level the match.
Costa became the fifth player to come from two sets to love down twice within a single French Open and the first player to win three consecutive five-set matches here since Kuerten did it in 1997. He has been on court 11 hours, 56 minutes.
Ferrero has advanced to at least the semifinals in his three prior visits to the French Open. He raised his record on clay this season to 24-2.