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Victoria Azarenka prevailed in a tightly contested third-set tiebreaker to down top-seeded Serena Williams and win the $2.37 million Western & Southern Open in a classic championship match between the world's top two ranked players on Sunday.

The two-time reigning Australian Open champion Azarenka won four of the final five points of the deciding tiebreak to capture her 17th career ATP title with a 2-6, 6-2, 7-6 (8-6) victory that took nearly 2 1/2 hours on the hardcourts at the Lindner Family Tennis Center.

The triumph was only Azarenka's third in 15 career meetings with the 16-time Grand Slam titlist Williams, though one of those verdicts came on a hard surface at Doha back in February. Williams also defeated Azarenka in the finals of last year's U.S. Open.

"Obviously a big win," Azarenka said. "It was a great match. I'm really, really pleased with the way I pulled it out. It was a great battle. Nothing was given away. It was pure fight. I'm really happy."

Williams, fresh off a title in Toronto last week, appeared well on her way to another after dominating Azarenka in the opening set. The 31-year-old American star played poorly in the second, however, committing 26 unforced errors to let Azarenka even the match.

Azarenka later came up with a big break of Williams to grab a 4-2 lead in the third set, but the 2013 French Open champ roared back and broke Azarenka twice while taking the next three games to serve for the match.

Williams couldn't hold serve, however, as Azarenka knotted the set at 5-5 before the match eventually went to a tiebreaker.

Azarenka claimed four of the first six points of the tiebreak before Williams won the next three to hold a 5-4 edge. Azarenka rebounded too with back-to- back points with Williams serving to create match point, but Williams forced an error from Azarenka after returning serve to even things up once again.

The Belarusian standout came up with a winner on her next serve, however, before Williams hit a forehead return into the net to clinch the match for Azarenka.

Azarenka earned $426,000 for winning this event, part of the U.S. Open Series leading up to the upcoming fourth Grand Slam of the season. Williams collected $213,000.