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Unfairly, unbelievably, Serena Williams (search) was robbed of a point by an umpire's mistake at the U.S. Open, just like her sister was at Wimbledon. It happened in the opening game of the third set between Williams and Jennifer Capriati (search), who went on to win their Open quarterfinal 2-6, 6-4, 6-4 Tuesday night.

"I'm very angry and bitter right now. I felt cheated. Shall I go on? I just feel robbed," a composed Williams said, laughing a bit. "At first, I thought it was another Wimbledon conspiracy."

The match was tight and testy, the way it almost always has been during their 17 matches: contested calls, spiked rackets, some gamesmanship and strokes pounded with power. A lot of power.

Capriati played superbly, without a doubt, but what always will be remembered is the miscue by chair umpire Mariana Alves of Portugal. She awarded the point to Capriati after Williams hit a backhand that landed in — and was ruled good by the line judge.

"I don't need to see the replay. I know my shots. Not only was it in, it wasn't even near the line," said Williams, who couldn't defend her 2002 Open title because of left knee surgery that forced her to miss eight months. "But I'm not making excuses. I didn't lose because of that. I probably should have closed her out in the second set."

It was eerily reminiscent of Wimbledon, where Venus Williams (search) lost in the second round after Karolina Sprem was mistakenly awarded an extra point in the final-set tiebreaker. Venus didn't argue at all, saying later she was confused; chair umpire Ted Watts was kicked out of the tournament.

Alves won't officiate another match during the Open, said tournament referee Brian Earley, who acknowledged the overrule by Alves was wrong.

"I'd prefer she not umpire at my court anymore," Serena Williams said. "She's obviously anti-Serena."

Williams wound up losing that pivotal game, and though she did break right back, she was broken again to 2-1 and never recovered. TV replays also appeared to show at least two other incorrect calls that went against Williams in the final game, when Capriati needed three match points to serve it out.

"I didn't even, like, look at it. It was close. I was just going to what the umpire said," Capriati told the crowd afterward, drawing some boos and murmurs.

"Believe me, I've had things go against me many times, plenty of times. I deserve to get a call once in a while."

In the semifinals, the eighth-seeded Capriati will face No. 6 Elena Dementieva, who outlasted No. 2 Amelie Mauresmo 4-6, 6-4, 7-6 (1) in a match marred by 24 double-faults, 82 unforced errors, 36 break points, and 14 service breaks. Mauresmo would have clinched the No. 1 ranking if she had won.

After all the theater of Capriati-Williams, defending men's champion Andy Roddick assembled a matter-of-fact 6-3, 6-2, 6-4 victory over No. 18 Tommy Robredo to reach the quarterfinals. Roddick's next foe is No. 28 Joachim Johansson, who beat Michael Llodra 6-2, 6-3, 6-2.

Earlier, 2001 Open winner Lleyton Hewitt beat Karol Beck 6-4, 6-2, 6-2 for his 14th consecutive win, and Tommy Haas beat Tomas Berdych 7-6 (6), 6-1, 7-5, erasing three set points in the tiebreaker.

"I'm playing pretty solid tennis, day in, day out," said Hewitt, who like Roddick has yet to drop a set.

Williams hadn't either until Tuesday, but she was broken to start the second set when Capriati hit a deep return that forced a forehand wide.

"I fought hard, and I prevailed because of that," said Capriati, who lost 6-1, 6-1 to Williams at Wimbledon but on Tuesday narrowed her head-to-head deficit to 10-7. "One point, I don't think, changed the match."

It was their third straight quarterfinal at a Slam, and much like Venus Williams' loss to Lindsay Davenport in the fourth round Monday, this one could have been for the title. For the first time since 1998, both Williams sisters will end a season without a single Grand Slam title between them.

Serena Williams has won six majors — including two at the U.S. Open — and Capriati has won three — though she's never been to the final at Flushing Meadows.

Capriati dug deep in the second and third sets, playing brilliant defense by scrambling along the baseline to extend points until Williams made a mistake. Williams finished with 57 unforced errors, 29 more than Capriati. Those allowed Capriati to get by with only 12 clean winners.

Williams had 25 winners officially, but that really should have been 26. Serving at deuce to open the last set, Williams smacked a backhand down the line, on the far side of the court from the chair umpire.

TV replays showed the ball landed in, by an inch or more, and the line judge called it correctly. But as Williams walked to the baseline to serve, dribbling the ball with her racket, Alves overruled that call and announced: "Advantage, Capriati."

A stunned Williams looked up and asked, "What happened?" Then, with hand on hip, she said to Alves: "That's my point. That ball was in. It's my advantage."

Williams swiveled to look at her parents and sisters in the guest box, then walked toward Alves, saying: "No, no, no, no, no. That was my point! What are you talking about? What's going on? Excuse me? That ball was so in. What the heck is this?"

Then Williams placed a ball on the court, and pleaded her case while pointing: "The ball landed here. That ball was not out. Are you kidding me? I'm trying to tell you: The ball was not out. Do I need to speak another language?"

Alves responded: "Please calm down."

Capriati stood at the other end, shaking her head. On the next point, she sailed a backhand long on a 14-stroke rally — which should have ended the game for Williams. Instead, it sent the score back to deuce, and Capriati capitalized with a tremendous volley winner to get another break point, converted with a forehand that tripped off the net cord and landed in.

She showed far more grit than she did in her epic semifinal loss to eventual champion Justine Henin-Hardenne last year at the Open, when Capriati was two points from victory 10 times.

"You get second chance after chance after chance," Capriati said. "I don't care what the tennis looks like, as long as it's gutsy."