• Australian Open, Day 10

Serena slayed by Stephens

Victoria Azarenka hits through a forehand © Getty Images

Enlarge

Victoria Azarenka battled back to power into the semi-finals of the Australian Open, but there was a huge shock later in the day as Serena Williams was toppled by Sloane Stephens.

Azarenka survived a scare against Jamie Hampton in the third round and it was a similar story against Svetlana Kuznetsova who put up a real fight in the first set before falling 7-5 6-1.

Williams, who had steamrolled her way to the quarter-finals, was struck down by a back injury and Stephens took advantage to claim a famous 3-6 7-5 6-4 success.

Azarenka found herself on the back foot against the two-time grand slam champion as Kuznetsova raced into a 4-1 lead thanks to some quite brilliant attacking play. Errors, though, were mixed in with the brilliance for Kuznetsova and they began to mount as the set wore on and Azarenka rallied before taking it after a mammoth 77 minutes.

Taking the second set appeared to drain the belief from Kuznetsova who was sucked into a baseline battle and came off second best. Four breaks of serve came Azarenka's way in a second set that lasted only 30 minutes.

The drama continued on Rod Laver Arena in the second of the day's quarter-finals, as Williams was hit by a back problem and she was unable to overcome the injury and a belligerent Stephens who held her nerve to reach her first grand slam semi-final.

There was no sign of the drama that followed as the opening stanza was like the No. 3 seed's previous matches, one-way traffic. Williams blasted Stephens off court in 28 minutes.

Stephens is a battler in the mould of Williams and she seized her chance when the four-time winner was struck down by a back spasm.

It did not look good for Williams as her movement was restricted and her fearsome serve nothing more than a flick over the net. The trainer was called and a medical timeout taken. It resulted in Stephens taking an epic second set and Williams continued to struggle at the start of the third - she finished with a huge 48 unforced errors.

It's not clear if any sort of medication was administered, but the movement began to return and she found the zip on serve. It looked like she would battle her way through as she broke Stephens to lead 4-3. However, she unexpectedly allowed errors to creep in and Stephens converted a break point.

Williams teed off on the Stephens serve in the ninth game and worked two break points, but she failed to convert either of them and her teenage opponent held firm.

And with the winning post in sight, Stephens did not falter as she worked match points, which she took when Williams sent a forehand into the net - meting out Williams' first defeat since August of 2012.

© ESPN Sports Media Ltd.