Azarenka's path to the semis was by no means easy - she needed a third-set tiebreak to oust No. 7 Samantha Stosur in the final eight - but she looked like the fresher player as the semifinal wore on, almost certainly a byproduct of Sharapova's exhausting hard-hitting style that generates plenty of winners but also results in a rash of unforced errors.
Nowhere was that more evident than in Friday's semifinal, where she committed 10 double-faults and a whopping 42 unforced errors.
It was Azarenka who struggled early, unable to handle the blistering pace of Sharapova's groundstrokes. The world No. 1 made nine unforced errors while hitting just one winner as she dropped the opening set in 40 minutes. Sharapova masked five double-faults and 12 errors of her own with 10 winners and an 81-per cent first-serve success rate.
The tide turned immediately in the second set, as Azarenka finally figured out how to handle Sharapova's jackhammer of a forehand and fired back with some power of her own. Azarenka made just three errors in the set while hitting 10 winners and breaking Sharapova three times, securing the momentum as Sharapova's energy visibly waned.
After both women took a short break between the second and third sets to escape the sweltering Flushing Meadows heat, Sharapova repeatedly looked for the knockout punch in the deciding set - but never came close. She didn't even see a break-point opportunity as Azarenka's pinpoint serve forced her into repeated mistakes. Azarenka wore down the 2006 U.S. Open champion and finally ended the two-hour, 42-minute epic by breaking Sharapova for the fifth time.
In an incredible statistic, both ladies entered the match unbeaten in three-set tilts this season. Friday's result improved Azarenka to 12-0, while Sharapova fell to 12-1.
Sharapova reflected briefly on the loss after the match before setting her sights on something more pleasant:
"I'm looking forward to checking out the ice cream truck that's around the corner from my hotel. It's been haunting me."
Azarenka, meanwhile, will have her hands full with a healthy and dangerous Williams. The No. 4 seed leads the all-time head-to-head series 9-1, including a 5-1 mark on hardcourts.