NEW YORK -- One call made all the difference, saving U.S. Open defending champion Serena Williams in a tense tiebreaker, and breaking the spirit of Jelena Dokic.

	When challenged, Serena Williams responded Monday by dominating Australia's Jelena Dokic in the second set of a 7-6, 6-0 victory at the Open.

The way they reacted to that call, and the shift in momentum it heralded, told much about the qualities of a champion that Williams possesses, and that the sad-eyed Dokic still must find while she deals with her father's troubles.

Williams rallied from that point -- the second of three set points she saved in the first-set tiebreaker -- to thrash Dokic the rest of the way, 7-6 (7), 6-0, Monday and move into the quarterfinals.

They had gone toe-to-toe throughout the first set, neither yielding on serve, until they arrived at 6-6. Williams had already pumped in 10 of the 14 aces she would accumulate, but the smaller and quicker Australian was even more efficient without the same power, giving up fewer points on serve.

Williams jumped to a 4-1 lead in the tiebreaker, only to see Dokic snap back with five straight points for a 6-4 lead. A solid forehand volley allowed Williams to save the first set point. Then came the critical call.

At the end of a long rally that had both players scurrying side to side, Dokic drilled a backhand crosscourt that a linesman signaled wide to make the score 6-6. Dokic argued to no avail with the umpire, then walked with her head and shoulders slumped to the other side of the net.

She would get another set point by running down a poor drop shot by Williams and whacking it crosscourt for a winner, but that was the end of Dokic's threat. Williams saved that third set point with a backhand volley that Dokic couldn't handle, then won the next two points, punctuating a strong backhand return with a loud "Yessss!" when Dokic netted the ball.

That was all Williams needed as she watched Dokic tank the second set, winning only three points on serve, spraying five times as many unforced errors as she had the first set, and looking as if she wanted to catch the next flight back to Australia to prepare for the Olympics.

Would Dokic have played differently, even won the match, if she had gotten the call at 6-5 and won the tiebreaker?

"Yeah, for sure, definitely," she said. "If I would have won that first set, maybe I would have won the match in two sets. You get on a roll, you've won the set. The pressure's on her. You know, she's the defending champion. You start getting a few back on her serves, you get into the points, she gets a bit tight."

Instead, Dokic virtually gave up.

"It's always hard to come out and play the next set when you've lost such a tight first set," she said. "You feel like, 'I've gotten so close to winning that set."'

It's an attitude that Williams doesn't share.

"My reaction going to the next set," Williams said of the times when she loses the first set, "is make sure I get the first game, break the next. Then all I have to do is hold, break, hold, break. I never give up. I can never see myself in a losing position, so I just keep going.

"If I had lost the tiebreak, I would have come out even stronger in the second set because I tend to play a little better when I'm down. That's just the way I am."

Mary Pierce, seeded No. 4, took a medical time-out while trailing 5-4 in the first set. After the trainer massaged her right shoulder, she returned to center court to serve. But she double-faulted on set point, giving Huber the set, 6-4.

Pierce immediately walked to the chair and retired from the match.

"The day before yesterday, after my match with Lisa Raymond, I was 100 percent," Pierce said. "In doubles it got sore and it was sore today. Every serve I hit it got worse."

Serena Williams had nearly her whole family in the courtside guest box, including big sister Venus, who is also in the quarters and could meet her in the final.

Dokic had no one, with her father and coach, Damir, banned from the premises after a drunken outburst in the players lounge cafeteria last week that caused him to be thrown out. The WTA Tour is considering whether to ban Damir Dokic from all tournaments, as it did several years ago with Jim Pierce, Mary Pierce's father.

"Whatever the decision is, I'm just going to have to deal with it when it comes to that," Jelena Dokic said. "You've got to be able to play yourself. No one's going to play out there for you. I'm just going to have to go on and just play tennis, do everything we've been working on, and talk about what I'm going to do."

Shortly after the Williams-Dokic match, rain delayed play for the second straight day. When the matches resumed, Todd Martin finished off a 7-6 (5), 6-3, 6-2 victory over 10th-seeded Cedric Pioline.

Martin won two sets and was leading in the third Sunday night before rain postponed the end of the match.

Also moving into the quarters were top-seeded Martina Hingis, who completed a match that was delayed because of Sunday's storms, beating No. 11 Sandrine Testud 6-2, 6-1. It was her 12th consecutive victory and sixth this year against the French player, who has never defeated her.

Next for Hingis is former champion Monica Seles, who reached the quarters Sunday night by defeating old foe Jennifer Capriati.

Elena Dementieva also advanced, defeating former NCAA champion Lilia Osterloh 6-3, 6-7 (4), 7-6 (5). She gets No. 10 Anke Huber, who moved on when French Open champion Mary Pierce pulled out after one set, unable to overcome recurring pain from a shoulder injury that sidelined her most of the summer.