Victoria Azarenka of Belarus hits a return to Samantha Stosur of Australia during their women's singles quarterfinals match at the U.S. Open. (SHANNON STAPLETON/REUTERS)

After crushing four successive opponents without surrendering a set, Victoria Azarenka finally got what she’d been looking for at the U.S. Open on Tuesday: A fight.

And it did more for her game than any of the lopsided victories that preceded it, forcing the 23-year-old from Belarus to fend off seven break points, shake off a garish double-fault in the decisive, third-set tiebreaker and produce her boldest tennis of the tournament.

“I enjoy the struggle — that pain we go through, that incredible moment that you feel relieved after you gave it all in every point you had,” Azarenka said after subduing defending champion Samantha Stosur, 6-1, 4-6, 7-6 (7-5) to advance to her first U.S. Open semifinal.

With the victory, Azarenka assured herself of retaining the world No. 1 ranking regardless of how she fares against her next opponent, 2006 U.S. Open champion Maria Sharapova or 11th seed Marion Bartoli, whose quarterfinal was suspended by rain with Bartoli leading 4-0 in the first set.

As Azarenka burst into a celebratory dance, the crowd at Arthur Ashe Stadium cheered, though it was unclear whether they shared her elation or were simply relieved that she had finally stopped shrieking.

Until this season, Azarenka had primarily been known for the brute force of her groundstrokes and the high decibel wail she emits each time she pummels the ball. But she has established herself as one of the sport’s more lethal hard-court contenders, fueled by a competitive fire that rivals that of Sharapova and Serena Williams, regarded as the favorite to win her fourth U.S. Open this weekend.

They have been the season’s dominant players, splitting the three majors to date (Azarenka winning the Australian; Sharapova, the French; and Williams, Wimbledon). They also swept the medals at the London Olympics (Williams winning gold; Sharapova, silver; and Azarenka, bronze).

“Being first time in the semifinals in the U.S. Open is incredible feeling for me,” Azarenka said in her post-match interview. “Definitely I don’t want to stop. I really want it bad.”

Asked later what it was exactly that she wanted—whether a U.S. Open title, multiple Grand Slam titles or the world No. 1 ranking—Azarenka reflected for a moment and then confessed that what she really wanted was everything.

“I feel like I will never be satisfied sometimes,” Azarenka said. “Even though I’m at the peak of my career right now, I feel like I want to do better. I want to do better.”

This is what defines champions. And this is why Azarenka relished being pushed and challenged by Stosur, 28, who regrouped impressively after a poor start to steady her shaky serve and answer Azarenka’s pace in kind. She muted the Belarusan’s attack with flat, deep groundstrokes struck to opposite corners of the court.

“She really pushed me to dig deep,” Azarenka said, her face flushed from all the running she did in the two hour, 23 minute match.

Facing a break point at 5-5 in the third set, Azarenka blasted her only ace of the match. Stosur then held serve to force the tiebreaker.

But after working so hard to level the match, Stosur committed a rash of unforced errors to hand Azarenka a 4-0 tiebreaker advantage. Two points from victory, serving at 5-3, Azarenka then hit a second serve nearly 10-feet long. Stosur drew even, 5-5, with an overhead. And Azarenka flicked a backhand drop shot that Stosur had no chance of reaching.

“I had to do something to surprise,” Azarenka said, “because at this moment you have to come up with something different—not the usual what you do.”

It was the sort of battle women’s tennis has too often lacked in recent years. The points were won outright, rather than conceded. With each swing of momentum, Azarenka and Stosur challenged themselves to play higher risk tennis rather than wait for the other to make a mistake.

“I kept telling myself, ‘Don’t be a chicken! Come on! Just go! Go for your shots!’” Azarenka said.

With rain arriving in waves, it was the only singles match completed Tuesday.

When the heaviest downpours scuttled the afternoon session, Sharapova trailed Bartoli 0-4.

And in a men’s match that was completed Tuesday night on Louis Armstrong Stadium, Spain’s David Ferrer defeated Richard Gasquet 7-5, 7-6 (2), 6-4 to advance to the quarterfinals.

Tournament officials announced that the Sharapova-Bartoli match would be continued Wednesday, making Ashe available for the night’s feature match, pitting American Andy Roddick against Juan Martin del Potro, weather permitting.