Sloane Stephens stunned after upsetting Serena Williams

MELBOURNE, Australia Fresh off her upset of Serena Williams in the Australian Open, American Sloane Stephens was in a state of shock. The magnitude of the 19-year-old's accomplishment only hit her while she was warming down after the match.

"I was stretching, and I was like, `I'm in the semis of a Grand Slam.' I was like, `Whoa. It wasn't as hard as I thought,"' she said. "To be in the semis of a Grand Slam is definitely a good accomplishment. A lot of hard work."

Stephens outplayed Williams, whose movement and serves had been slowed by a back injury, and beat the 15-time Grand Slam champion 3-6, 7-5, 6-4. It was Williams' first loss since Aug. 17, and her first defeat at a Grand Slam tournament since last year's French Open.

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The No. 29-seeded Stephens hadn't been given much of a chance of beating Williams, who lost only four matches in 2012 and was in contention to regain the No. 1 ranking at the age of 31.

Williams' latest winning streak included a straight-set win over Stephens at the Brisbane International this month.

Stephens wasn't even sure that she could beat Williams until she woke up Wednesday.

"When I got up, I was like, `Look, Dude, like, you can do this.' Like, `Go out and play and do your best," she said.

Williams walked around the net to congratulate Stephens, who then clapped her hand on her racket and waved to the crowd, a look of disbelief on her face.

Stephens has said she had a photo of Williams in her room when she was a child, and had long admired the Williams sisters.

"This is so crazy. Oh my goodness," Stephens said, wiping away tears in her post-match TV interview. "I think I'll put a poster of myself (up) now."