Azarenka went to the locker room for medical treatment -- the tournament confirming later it was for left knee and rib injuries -- after dropping serve in the ninth game then returned to break the 29th-seeded Stephens' serve to finish off the match.
"Well I almost did the choke of the year right now at 5-3 having so many chances I couldn't close it out," Azarenka said in an on court TV interview. "I just felt a little bit overwhelmed. I realized I'm one step away from the final and nerves got into me for sure."
The crowd had tried to get Stephens back into the match in the second set. Fans yelled encouragement after almost every point and a few in the crowd heckled Azarenka by mocking the noise she makes when she hits the ball.
Azarenka started to lose her composure when she hit a forehand way over the baseline on her third match point, her hooting sound elevating to a louder, high-pitched shriek.