World No. 1 Serena Williams may hold a 12-3 career record against world No. 2 Victoria Azarenka, but Azarenka has won two of their last three matchups.
As well as Williams has played this year, Azarenka has a chance to uproot the 16-time Grand Slam singles champion on Sunday for the 2013 U.S. Open trophy.
There is no question that Williams is the best women's tennis player in the world right now. She was 60-4 with eight singles titles this year headed into the 2013 U.S. Open. That included a French Open title.
But Azarenka isn't half-bad, either.
The 24-year-old was 36-4 with three singles titles this year headed into the U.S. Open. She won the Australian Open, reached the semifinals at the French Open and now finds herself in the final at the U.S. Open.
She's won her last two matches in straight sets. That includes holding off formidable underdog Flavia Pennetta in straight sets on Friday, 6-4, 6-2. Pennetta had defeated No. 4 seed Sara Errani, No. 27 Svetlana Kuznetsova, rising No. 21 seed Simona Halep and No. 10 seed Roberta Vinci before her loss to Azarenka.
When looking at the last three matchups between Williams and Azarenka—all played this year—there is a noticeable difference between Azarenka's two wins and one loss.
It all comes down to what Azarenka does on her serve.
In her wins against Williams in Doha and Cincinnati this year, Azarenka won at least 58 percent of first-serve points and at least 56 percent of total service points, via WTATennis.com.
In her loss to Williams in Rome, Azarenka won 50 percent of first-serve points and 43 percent of service points.
Azarenka won 40 percent of return points in her loss to Williams in Rome and in her win against Williams in Cincinnati. She noticeably holds up against Williams' serve win or lose, but—at least lately—she must take advantage of service games to defeat the historic 31-year-old.
While Azarenka defeated Pennetta in straight sets on Friday, it had more to do with her return game than her serve. She won a ho-hum 57 percent of first-serve points and 34 percent of second-serve points while committing six double faults, but captured 67 percent of total return points, via USOpen.org.
We all know about Azarenka's return game, but if she is to upset Williams on Sunday, she is going to have to play more like she did against Daniela Hantuchova and Alize Cornet, and less like she played against Pennetta and Ana Ivanovic.
It all begins and ends with Azarenka's serve.