Victoria Azarenka defended herself against a storm of criticism Thursday after she took a medical time out at a crucial stage of her Australian Open semi-final defeat of teenager Sloane Stephens.

Azarenka's surge into the final against China's Li Na was overshadowed by a controversial 10-minute break when she left Rod Laver Arena for treatment on a rib complaint that was giving her back pain and breathing difficulties.

When she left the court, Azarenka had just blown five match points, and America's Stephens, 19, was left waiting to serve to stay in it. When Azarenka returned, she broke the teenager to win 6-1, 6-4 in 1hr 41min.

Immediately after the match, Azarenka said she had avoided "the choke of the year" and "felt a bit overwhelmed", sparking suspicions she had called for the time out to gather her thoughts.

Azarenka was accused of gamesmanship by respected commentator Pam Shriver and her colleague at ESPN, Patrick McEnroe, called it an "absolute travesty" on Twitter. But the 23-year-old maintained the injury was legitimate.

"I had been struggling a little bit throughout the whole match, from the second set with my back," she said.

"And it just kept getting worse. I should have called the trainer a little bit earlier, before I got to the point that I couldn't really breathe and had to go off the court.

"So there was a little bit of, my bad. But a rib got locked and kept getting worse. I had to have it adjusted. I really had to go and have that medical time out."

She added: "It was a necessary thing for me to do. I just regret that I didn't take it earlier, that it got to the point that it was pretty much impossible for me to breathe and to play."

Stephens, who was playing her first Grand Slam final and shares an agent with Azarenka, refused to criticise the Belarusian.

"If it was one of my friends, I would say, 'Oh my God, that sounds like a P-P', which is a personal problem," Stephens said.

"Other than that, it's just unfortunate. I did lose the next game but I wouldn't say the medical time out is why I lost the next game."

Australian Open tournament director Craig Tiley told 7 in an exclusive that, on the evidence on the doctor who treated Azarenka and the trainer who treated her, that everything was above board.

"Certainly when these things happen and the trainers are called to the court the referee and myself we have a conversation," he said.

"In this instance the doctor confirmed he did treat the rib, he did treat the knee and once he made that assessment she was able and ready to continue play."

Former players raced to Twitter to air their thoughts, with many calling Azarenka's actions not in the spirit of the game.

But Tiley said the only person's opinion that really mattered was Stephens.

"We really have to ask Sloane Stephens... what she felt and how it affected her as a person, but everything was in the rules of the game and Sloane did make a comment that she [Azarenka] was able to continue on," he said.

However, the incident is likely to raise questions about possible manipulation of time outs, which are used to treat injuries in the middle of a match.

Azarenka said her initial comments, given in an on-court interview, had simply been misunderstood. And she insisted the reason for the time out was genuine.

"Honestly, I cannot say about anybody else," Azarenka said. "I can only speak about myself. I'm being really honest here, what I'm talking about. When I play and somebody takes a medical time out, I don't doubt them."

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