KEY BISCAYNE, Fla. — On a sunny day in South Florida, the future of American women's tennis seldom looked so gloomy.

The present's in good hands thanks to Serena and Venus Williams, but they were the lone U.S. females among the 32 players reaching the third round at the Sony Ericsson Open.

Top-ranked Serena won 6-2, 6-3 against 19-year-old Californian Alexa Glatch, who conceded her generation has yet to produce a player worthy of succeeding the Williams sisters.

"There is a gap there right now," Glatch said. "You can't deny that. It's very tough out here."

No. 5-seeded Venus Williams also won her opening match, beating Shahar Peer 6-3, 6-3. Seeded players had first-round byes.

It was hardly a banner day for American men, who went 0-5, with all the losses in three sets. Sam Querrey, John Isner, Amer Delic and Bobby Reynolds were beaten by seeded opponents, and No. 27 Mardy Fish also lost, leaving four U.S. males to start the third round Sunday.

The showing by American women is hardly a surprise, because only four are ranked in the top 100, and the Williams sisters are the lone U.S. players in the top 30. No American teenager is being heralded as a future Grand Slam champion, and former No. 1 Lindsay Davenport said the situation is worrisome.

"We don't really have anyone right now," Davenport said. "If you look at the rankings, with only Venus at age 28 and Serena at 27, it's not a good state."

The state of Serena's game is just fine, however. She needed only one swing to reassert her superiority at the tournament where she's most dominant, pulling a return winner crosscourt on the first point to make a quick impression on Glatch.

"She just nailed it," Glatch said. "I don't think I even saw it. I was like, 'OK, here we go.'"

An hour later, there Glatch went. For Williams, the victory was the first step in her bid for a record sixth Key Biscayne title.

Her older sister started more slowly, losing 12 of the first 14 points before taking charge by winning six games in a row.

"I haven't played in almost four weeks, so just a little bit of a slow start," Venus said. "But I always felt confident."

Venus is a three-time Key Biscayne champion, although her most recent title came in 2001.

On the men's side, Fish lost to Nicolas Massu 5-7, 7-6 (4), 6-2 in a rematch of the 2004 Olympic final, which Massu also won. Querrey was beaten by No. 32-seeded Feliciano Lopez 6-7 (5), 7-5, 6-2; Isner lost to No. 11 David Ferrer 6-3, 3-6, 6-2; and Reynolds was defeated by No. 18 Radek Stepanek 7-5, 6-7 (3), 6-2. Delic lost a night match to No. 17 Marin Cilic 6-3, 6-7 (7), 6-3.

Top prospects among American women include 17-year-old CoCo Vandeweghe, 17-year-old Julia Boserup and 16-year-old Christina McHale. None is ranked higher than No. 381, and only Vandeweghe played in the main singles draw at Key Biscayne, losing in the first round.

"They're all at that age where a lot of players by that time are winning a lot of matches," Davenport said. "I'm hopeful if one breaks through, the rest will kind of follow her lead."

Even older is Glatch, who has made progress in fits and starts. She was the U.S. Open juniors runner-up in singles and doubles in 2005, but soon after that a motor-scooter accident sidelined her for nine months.

She's now ranked a career-high 124th, yet still needed a wild card to enter Key Biscayne. She smiled when asked if she's the face of the future for American tennis.

"I could be. I could not be," Glatch said. "You never know. I got that question asked to me many times when I was younger, but not lately."

Serena Williams remembers being 19 — she was already a U.S. Open champion. But she said it's too early to count out Glatch and her contemporaries.

"I definitely think there will be some players who will emerge," Williams said. "I think it's inevitable."

Glatch didn't rise to the occasion in her first meeting with Williams. The youngster had brief hope with two breakpoint chances to reach 4-all in the second set, but a not-ready-for-prime-time forehand repeatedly betrayed her.

"I don't think I played my best tennis, not even close, probably," Glatch said. "And I don't think she did either. It was kind of an ugly match. We were both a little shaky out there."

Serena confessed to butterflies even though she has lost only one match at Key Biscayne since 2001.

"Just a little jitters going out there," she said. "You know, the first match no one wants to go out."

Especially when American tennis is counting so heavily on your family.