Then again, that's what makes a true upset.
The top-ranked player in the world, Williams has not dropped a set this tournament as she vies for her 17th Grand Slam title. Playing some of the best tennis of her illustrious career, Williams looks like the smart bet to win this year's U.S. Open.
But they play the matches for the season, and No. 2 ranked Azarenka is no slouch with her racket. The 24-year-old from Belarus fought through some difficult three-set bouts in the middle of the tournament but breezed through her last two contests.
When these two met last year in Queens with the same trophy hanging in the balance, Azarenka fell short in a tightly-contested third set. What can she do to engineer a different result this time?
Where: USTA Billie Jean King National Tennis Center in Flushing Meadows, N.Y.
When: Sunday, Sept. 8 at 4:30 p.m. ET
Control the Serve
A major strength for Williams has confounded Azarenka for parts of the tournament. For Azarenka to have any chance at besting Williams, she'll need to corral her serve.
Despite defeating unseeded Flavia Pennetta during the semifinals, Azarenka's serve broke five times, and she hardly dominated by winning 57 percent of her first serve points to Pennetta's 48. Her six double faults won't fly against Williams, who is good enough to win without Azarenka making matters easier.
Hosting another clinic in her semifinals victory over fifth-seeded Li Na, Williams claimed 76 percent of her first serve points with only one double fault. In her clean sweep over Carla Suarez Navarro in the quarterfinals, Williams won an unfathomable 88 percent of her first serves.
When Azarenka defeated Williams in their last match, she soared to a 73 first-serve percentage while limiting Williams to 59. Her serve cannot falter, and her return game must be at its finest.
Azarenka can't let Williams bully her in the serve game, otherwise it could be a long day for the underdog.
Get Ahead Early, Play Her A-Game
Twice this tournament Azarenka has rallied from behind after squandering the opening set. She better not try her luck again on Sunday.
Azarenka dusted off early deficits versus Ana Ivanovic and Alize Cornet, but neither ranked competitor can touch Williams, who is showing no signs of wearing down at age 31. If Azarenka places herself in a hole, she's unlikely to ever climb out of it.
In order to gain the early advantage, Azarenka will have to come out firing on all cylinders. It's a scenario Williams is prepared for, as she told SI.com's Richard Deitsch that her rival performs at her apex in their clashes.
"I definitely feel like when she plays me she plays her best by far," Williams said. "I have seen her play other players, and when I play her, I'm playing a totally different player. Obviously she brings her best game."
There is past precedence to present the younger competitor with some hope of topping her veteran adversary. While Williams has dominated the overall head-to-head series with a 12-3 edge, Azarenka won their past two battles on a hard court surface.
Nevertheless, Azarenka must support Williams' theory and play on a higher level to have any shot at claiming her first US Open title.