There was a thrilling audacity about what Serena and Venus Williams attempted at Wimbledon this year.

Sidelined by illness and injury for 11 and five months, respectively, the Williams sisters chose the sport’s grandest stage to return to competition with only minimal preparation.

The decision was much like their shots: bold and full of risk, given their sterling resumes at the All England club, where they have combined to win nine of the last 11 Wimbledon titles. Yet an all-Williams final looked increasingly plausible even amid its implausibility.

Their march to the final was halted in unequivocal terms Monday by less imposing players who have neither a Grand Slam title nor appreciable name recognition between them. As a result, the Wimbledon’s women’s quarterfinals will be without an American for only the third time since Grand Slam tournaments agreed to allow professionals compete alongside amateurs back in 1968.

Serena, Wimbledon’s defending and four-time champion, was ushered off by Marion Bartoli of France, 6-3, 7-6 (8-6). Venus followed 1 hour 40 minutes later, turning in an error-strewn performance against Tsvetana Pironkova, the Bulgarian who beat her by the same score, 6-2, 6-3, at Wimbledon last year.

With Venus 31 and Serena three months shy of her 30th birthday, it’s difficult to imagine they can reclaim world-beating form many more times, if ever.

“It’s hard to come back the older you are — physically and mentally,” said former pro Mary Joe Fernandez. The Williams sisters “have done it before successfully. And I’m sure we’re going to see another good run by both of them. But it’s harder to recover and harder to stay positive.”

Unless the sisters reclaim a place among the top 10 and sustain it, the United States likely is in for a fallow period in women’s tennis.

“We’re not going to see any number-one players [apart from the Williams sisters] for another four or five years,” Chris Evert, a three-time Wimbledon victor, said bluntly in an interview Monday. Evert now runs a tennis academy in South Florida and keeps an eye on prospects in the pipeline.

“When I’m at my academy . . . I look at what’s around there,” Evert said. “Really, the 15- and 16-year-olds are good, but I don’t see any 18- or 19-year-olds. I see four to five years before we see somebody. That’s not to say these players can’t be top 20, but I don’t see any number ones.”

Wimbledon’s early rounds underscored the stark reality. The 128-player women’s field included 12 Americans. Their ranks were culled quickly. Only three (the Williams sisters and Bethanie Mattek-Sands) advanced to the second round. Only the sisters made it to Round 3.

The prospects aren’t as bleak for American men. Minnesota native Mardy Fish, 29, toppled sixth-seed Tomas Berdych of the Czech Republic 7-6 (7-5), 6-4, 6-4 on Monday to earn a spot in the quarterfinals for the first time in his career.

And the losses by Serena and Venus, seeded seventh and 23rd, weren’t as shocking as the defeat of No. 1 seed Caroline Wozniacki, who fell Monday to Slovakia’s Dominika Cibulkova, 1-6, 7-6 (7-5), 7-5.

That leaves Maria Sharapova, who advanced 6-4, 6-2 over China’s Shuai Peng, as the only past Wimbledon champion left in the women’s draw.

For women’s tennis to capture the attention of American sports fans, it needs to produce the rivalries and personalities that mark men’s tennis. And without the Williams sisters in the mix, they are in short supply.

The fact that either Williams reached Wimbledon’s fourth round was impressive.

Serena’s last Grand Slam event was Wimbledon 2010. She cut her foot on broken glass in a freak accident shortly afterward and underwent two surgeries to repair ligament damage. Then, this spring, she suffered a pulmonary embolism and underwent emergency surgery to remove blood clots from her lungs.

She returned to competition just two weeks ago at a grass-court tournament in Eastbourne and went out in the second round. Venus, who hadn’t competed since withdrawing in the third round of January’s Australian Open with a hip injury, returned at the same tournament and lasted three rounds.

But Monday, Serena was knocked on the defensive by the 5-foot, 6-inch Bartoli. The ninth-seeded Frenchwoman has an idiosyncratic style, hitting two-fisted backhands and forehands that are tricky to read. Despite a hitch in her service motion, she hit more aces (10) than Serena (eight).

And though Serena fended off four match points, Bartoli refused to wilt.

Unlike Serena, Venus was never in contention.

“Today I missed some overheads, swinging volleys — shots I never miss,” Venus said. “It’s just not easy to find the rhythm right away.”

The sisters remained unbowed in defeat, declaring themselves pleased with their performances, given their limited preparation. Both said they look forward to the upcoming hard-court season. The next match for both will be in Washington, for the Washington Kastles, in July. And they vowed to come back stronger.

“With more time, I think I can definitely play better,” said Venus, who committed 16 unforced errors (as opposed to 20 winners) in the loss to Pironkova. “Obviously I would have loved to have peaked here. But, you know, I’m moving on.”

Said Serena: “I can only get better. And that can potentially be really scary because I can only go up from here, and I can just do so much more.”

Although the departure of the Williams sisters took some of the luster from the second week of the women’s tournament, longtime students of the game remained upbeat.

“The women’s draw going into today had great promise. And certainly today took a lot off the charisma and appeal,” said former pro Pam Shriver. “But having said that, there are actually great story lines everywhere.”

Even so, Sharapova is the lone known commodity among them.

In addition to Bartoli, Pironkova and Cibulkova, the other quarterfinalists are Sabine Lisicki, Tamira Paszek, Victoria Azarenka and Petra Kvitova.

Confessed Evert: “I mean, I’ve been away from the game, but I didn’t know these girls at all! I had to learn quickly. They’re coming out of the woodwork now!”