New York, United States: Defending champion Sloane Stephens reached the fourth round of the US Open on Friday with a 6-3, 6-4 victory over former world number one Victoria Azarenka.
Stephens, unseeded in her fairytale run to a first Grand Slam title here last year, is now at No. 3 the highest-ranked woman left in the draw after the exits of world number one Simona Halep and number two Caroline Wozniacki in the first and second rounds.
Stephens was expecting a battle against two-time Australian Open winner Azarenka, playing on a wildcard invitation as she works her way back towards the top after time off to have a child.
An early break gave Stephens breathing room in the opening set, and she put it away by breaking Azarenka at love in the ninth game.
But the Belarusian's big shots stretched Stephens' vaunted defensive skills to the limit in the second set as the American's early break for a 3-1 lead was followed by an exchange of three more breaks before Stephens closed it out by breaking Azarenka in the final game.
"I competed. When things got tough, I just hung in there, battled as hard as I could, ran down every ball," said Stephens, who wasn't surprised to see Azarenka raise her game in the second set.
"I think what happened is I was playing a former Grand Slam champion -- she raised her level.
"I just had to stay in it and I did that very well," added the 25-year-old, who added an apology to coach Kamau Murray for upping the anxiety level.
"I think he stroked out twice, I'm sorry man," she said.
The match was halted briefly and the players allowed to leave the court as the stadium roof was closed for the first time this week when showers arrived with Azarenka up 4-3 in the second set.
Stephens said she benefitted from the break, during which she changed clothes and came back feeling refreshed.
"I think that helped me a lot," said Stephens, who won the last three games in the "super-cool" atmosphere of the closed stadium.
"It kind of felt like a night match with the lights on and everything," she said.
Stephens will face 15th-ranked Belgian Elise Mertens for a quarter-final berth. Mertens withstood a late challenge to beat Czech veteran Barbora Strycova 6-3, 7-6 (7/4).
"I played her last week in Cincy," said Stephens, who fell to the Belgian in the third round in Cincinnati. "I'm going to give it another go."