KEY BISCAYNE, Fla. (AP) -- It was easy to see that fiery Lleyton Hewitt was off his game Friday night, because he did little fist-pumping or chest-thumping during his match -- and none when it ended.

The top-ranked Hewitt, left vulnerable by an upset stomach and wobbly groundstrokes, lost his opening match at the Nasdaq-100 Open to Francisco Clavet 6-4, 6-4.

Hewitt's nausea notwithstanding, the result was a stunner because Clavet came into the tournament without a victory this year. At 34 he's the oldest player in the draw and plans to retire at the end of the year.

A qualifier from Spain, Clavet is ranked 178th. It has been nine years since a No. 1 player lost to someone ranked so low, which didn't make Hewitt feel any better.

The Australian blamed his ailment on a room-service meal he ate at his hotel Thursday night.

"I didn't feel great out there,'' he said. "I was sick as a dog all night. It came quick after I had dinner. I was feeling 100 percent before that.''

Hewitt, who will remain No. 1 despite the loss, twice received treatment from a trainer during changeovers. But smelling salts didn't help.

"I was still sick, and it got worse as the match went on,'' he said.

Andy Roddick struggled too, but overcame some sloppy shotmaking and harrowing moments to defeat qualifier Cyril Saulnier 6-7 (1), 7-6 (2), 6-4.

The sixth-seeded Roddick led a parade of American men into the third round. Mardy Fish upset 11th-seeded Sebastien Grosjean 6-4, 7-6 (3), and wild card Robby Ginepri ousted No. 16 Alex Corretja.

Countrymen James Blake and Todd Martin also won. Jan-Michael Gambill, Vince Spadea and Taylor Dent lost.

On the women's side, top-seeded Serena Williams battled illness herself but overcame stomach flu to beat Francesca Schiavone 7-5, 6-1.

"At one point I didn't think I'd be able to go on,'' Williams said. "I couldn't even walk Thursday.''

Hewitt was in trouble from the start, falling behind 5-1, and he trailed most of the second set as well. He served poorly and repeatedly missed putaway opportunities.

Clavet beat the scrambling Aussie at his own game, smartly mixing the pace, racing from corner to corner chasing down shots and finally causing an unforced error. Hewitt made 33, compared with 14 for the Spaniard.

"He's the best defensive player in the world,'' Clavet said. "He's unbelievable, very fast. So I had to try to mix up my game to play some slice, some topspin, slow balls and then suddenly accelerate. I tried to make him attack me, because he doesn't like to do that.''

A stunned stadium waited for a comeback that never came.

"Vamos, Lleyton!'' one fan shouted, but there was no rousing Hewitt from his languor. The upset ended his 12-match winning streak, which included a title at Indian Wells earlier this month.

Roddick said he has felt lethargic for several days, but unlike Hewitt, he fought off the blahs. It helped that several close calls and shots clipping the net cord went his way.

"I was pretty lucky today,'' he said. The 20-year-old Roddick will play the 32-year-old Martin on Sunday, while Blake will face Ginepri in another all-American matchup.

Two women seeded in the top 10 were eliminated: No. 5 Daniela Hantuchova failed two convert two match points, faded in the 90-degree heat and lost to Alicia Molik 2-6, 7-5, 6-0; and No. 10 Monica Seles withdrew before her first match, saying she hasn't fully recovered from a stress fracture in her left foot.

Seventh-seeded Lindsay Davenport beat Cristina Torrens Valero 6-2, 6-1.

Roddick served 17 games and held every time, saving seven break points, including two in the final game. But he broke only once against Saulnier, and that came when the Frenchman played a poor service game to give Roddick his first lead of the match at 3-2 in the final set.

"He gave me the game,'' Roddick said. "I didn't really do much.''

Roddick lost only 14 points on his first serve, and one 132-mph blast bounced into Saulnier's face. Roddick's fastest serve was a 140-mph winner to close out the second set.

Blake, seeded 21st, beat Fernando Meligeni 7-6 (5), 6-2. Ginepri rallied past Corretja 4-6, 7-6 (5), 6-2. Martin rallied to eliminate Andrei Pavel, who retired with a back injury trailing 6-7 (2), 6-4, 2-0.

Gambill lost to No. 12 Rainer Schuettler 6-2, 6-3, and 1998 champion Marcelo Rios routed Dent 6-1, 6-1. Spadea lost to No. 5 Carlos Moya 6-4, 5-7, 6-4.

Yevgeny Kafelnikov beat Jonas Bjorkman for the 11th time without a loss, 6-3, 6-3.