When the shock of Serena Williams's third-round loss at Wimbledon settled in Sunday, American tennis was left to confront some uneasy questions that had been lurking at the fringes of the sport for months.

Chief among them: Will Serena and her elder sister Venus ever dominate the women's game, either together or individually, as they did during that dazzling span from July 2001 to July 2003, in which they won seven of nine Grand Slam titles between them?

If not, do the sisters run the risk of being remembered less for rewriting the sport's history and more as a cautionary tale about the perils of relying too much on talent and too little on hard work?

And how, in turn, would their failure to reclaim their place atop the game affect the popularity of tennis in the United States, which has been on the decline for years, save for spikes when the Williams sisters take charge?

At 23 and 25, Serena and Venus are sufficiently young and gifted to script whatever sort of future they want in tennis.

But their showing so far at Wimbledon, which took its annual day of rest on the tournament's midpoint Sunday, has been far from promising, suggesting that the sisters either aren't sure they want to be the world's best anymore or they're unclear, in an era of increasing parity, how to go about it.

"I had it in my head those two could really dominate and change the course of tennis and rewrite tennis in a big way," said Mary Carillo, an NBC commentator and former touring pro, on the eve of the tournament. "It's so much up to them and how much they feel committed to being great."

Serena was ushered out of Wimbledon in straight sets Saturday by 85th-ranked Jill Craybas, who in nearly a decade as a pro had never advanced past the third round of a Grand Slam tournament. It was Serena's earliest Wimbledon exit since 1998, when she made her tournament debut at age 16.

Though Venus plays on to the fourth round, in which she'll face Craybas on Monday (rather than her sister), she hasn't looked sharp in her matches to date. On Saturday she was tested by 20th-seeded Daniela Hantuchova of Slovakia.

"Venus played terrible today, in my opinion," said Richard Williams, the girls' father.

Said Serena, "I think maybe she's feeling her way through."

Though shocking on one hand, the sisters' struggles were foreseeable.

Since winning the Australian Open in January (her seventh Grand Slam title), Serena played only 11 matches before heading to Wimbledon -- and none of them on grass. She withdrew from events because of ailments and injury, including a gastrointestinal illness, sore right shoulder and left ankle sprain, which she characterized last week as a hairline fracture. She also bowed out of events because of pride, saying she didn't want to compete if she didn't feel she could win.

Venus arrived at Wimbledon without much match-toughening, as well. Her only title this year, in Istanbul, came against a draw of relative unknowns. And a 15-year-old bounced her from the French Open in the third round.

Still, given the sisters' on-court resumes and well-known competitive fire, top-ranked Lindsay Davenport argues that it's far too early to conclude they won't get themselves back to the top.

"They have the games, and they have to ability to do that," said Davenport, 29. The problem "has been consistency and being able to play tournaments healthy. I think they have been plagued by quite a bit these last 18 months. Injuries, and the injuries led to some confidence problems."

Serena Williams insisted her loss to Craybas had nothing to do with her ankle.

"I had a lot of rust," she said. Serena Williams's serve, normally a weapon, deserted her. She was broken in her first five service games. And her punishing groundstrokes found the net or far side of the baseline too often. She finished with 34 unforced errors and 29 winners.

"I shouldn't have lost this match," Serena said tearfully. "I hate to waste time, and I worked pretty hard the last week or so. But I guess you got to work more than a week, you know."

As the Williams sisters sort out their priorities, former touring pro Leslie Allen feels their impact on tennis will remain strong.

"What they did is they brought a whole new audience to tennis," said Allen, who like the Williams sisters is black. "People who didn't traditionally look at tennis began to watch it. And they weren't necessarily people of color. Their reach was so broad, so universal because they were the atypical tennis player. They went from that country-club model, and had more universal appeal. They were interesting people; they wore interesting outfits; and they had dynamic games."

But there is reason to worry about who will succeed them. There aren't many American girls among the elite junior ranks, where tomorrow's top pros are cultivated.

"There are no young [American] women coming up, and that's a big concern," Carillo said. "We're seeing not just Russians, but Serbo-Croatians and Bulgarians, apart from [the traditionally strong] South Americans on the women's side. It's their best shot at becoming successful, at becoming rich, at becoming famous. And they're going after it in a way that doesn't seem to be happening in this country."

For those who want to see tennis thrive again in the United States, it's no time to sit still.

John McEnroe, for one, thinks it's time the game's power brokers -- including the U.S. Tennis Association, major broadcasters and players' organizations -- start promoting players more aggressively. And McEnroe argues that it's time players became more fan- and media-friendly by taking a cue from NASCAR, of all things.

"They seem to think that all they have to do is stick the players out on court," McEnroe said during a conference call. "But there's a lot more options [for sports fans]; there's a lot more channels. I happen to be a NASCAR fan. These guys lay their life on the line, but a half-hour before the race, they're out there signing autographs and speaking to the media. That's an incredible thing. The media respect that, and the fans love it. And for starters, the players need to do more of it."

Venus Williams, left, and sister Serena, who once dominated tennis, have had a hard time at Wimbledon. Serena Williams was ousted in the third round.