Tennis US Open: For the first time since 1998 neither Venus nor Serena Williams will end the year with a grand slam singles title in her possession writes Stephen Bierley at Flushing Meadows

However, it took a fallible umpire, plus a wonderfully fighting performance from Jennifer Capriati, to put an end to Serena's US Open under the Arthur Ashe floodlights, Capriati winning their quarter-final 2-6, 6-4, 6-4.

Venus had already lost in the fourth round to Lindsay Davenport, leaving her younger sister to walk the Williams line. These days the difficulty for both is that the standard they set at the turn of the millennium no longer guarantees them the success they had learned to take for granted.

In recent times injuries have undermined their dominance, robbing them of their aura of invincibility, while at the same time the rest of the world has gradually caught up. Between them the sisters won 10 majors between 1999 and 2003 - six for Serena and four for Venus - and played each other in six grand slam finals.

It would be foolish to write either of them off, although it is clear that both Americans must re-commit themselves to the game if they are to re-establish themselves. It will not be easy. Both are currently outside the top 10 and even Serena's protected number three seeding could not prevent her early exit on this occasion.

There was reason to argue that several terrible line calls undermined her confidence against Capriati at a crucial time in the deciding third set but such blatant errors could not disguise Serena's frailty under extreme pressure. Since her knee operation last year she has appeared more vulnerable, as was underlined in this year's Wimbledon final when she was beaten in straight sets by Russia's 17-year-old Maria Sharapova.

"It's been a tough road but I'm comforted by the fact that I shouldn't have been here anyway," said Williams, who had to pull out of the Olympics last month. "I've made a great effort but I really didn't have enough time to prepare." And, despite her obvious frustration over the line calls, Williams admitted that she had "dug my own grave, got in and covered myself with dirt".

Her controlled hitting in the opening set had been reminiscent of her straight-sets quarter-final victory over Capriati at Wimbledon this year. It seemed that, as on the grass, Capriati would be rushed to defeat but she steadied herself, concentrated on getting her first serve in by cutting back on the power and began to dictate the rallies. "I think I played like an idiot," said Williams.

The major mistake by the Portuguese umpire, Mariana Alves, came in the first game of the third set when Williams hit a backhand that fell well inside the line. Alves called the point in favour of Capriati, which led to a heated altercation, with Williams believing there had been an over-rule.

There were further close calls in the final game of the match, all of which went against Williams, although Hawkeye, used by television to point up errors, is far from infallible. Williams referred to Alves as being "anti-Serena". However, even as she claimed to be "angry, bitter and cheated" she could not stop herself laughing. "Should I keep going?" she said. "I just feel robbed."

The bottom line, and she knew it well enough, was not the umpire's howler but her own multiple errors: "I don't want to make excuses and say I lost because the umpire cheated me. It's not why I lost, I lost because I didn't play right and you've got to give credit to Jennifer."

As heavy rain in the New York area interrupted play yesterday the fallout from Capriati's controversial victory re-opened the debate over the use of video replays. Defending men's champion Andy Roddick, want technology to help umpires rule on tight line calls, especially as broadcasters here are using Hawk-Eye and Mac-Cam systems to show where the ball has landed. Roddick, who played immediately after the Williams-Capriati match says a situation similar to that in the NFL should be used, allowing players two challenges per match.

"I don't see a whole lot of downside in that," he said. "You're only going to do it if you're 100 percent sure.

"It would be pretty easy to have a monitor right at the side of the court."