Stephens stuns ailing Serena, Federer forges on

By Nick Mulvenney

MELBOURNE (Reuters) - Serena Williams went down smashing rackets and screaming as she bowed out of the Australian Open quarter-finals on Wednesday, hampered by a back injury and beaten in three sets by fellow American Sloane Stephens.

The injury robbed Williams of her serve - the most effective weapon in women's tennis - but teenager Stephens will take much credit for holding her nerve to finish off the ailing 15-times grand-slam champion.

Roger Federer's bid to emulate Williams as a five-times Melbourne Park champion survived a five-set test at the hands of an inspired Jo-Wilfried Tsonga and the Swiss marched on to a last-four meeting with Andy Murray, who crushed Jeremy Chardy.

Stephens will have 24 hours to prepare for her first grand-slam semi-final against defending champion and world number one Victoria Azarenka, who came through a minor scare to beat Russian Svetlana Kuznetsova.

"Oh my goodness," said Stephens, teary-eyed and almost lost for words after beating a player whose picture once adorned her bedroom wall. "This is so crazy, but oh my goodness, I think I'll put a poster of myself up now."

The 31-year-old Williams, odds-on favorite to claim a third successive grand slam crown, pulled up to avoid hitting the net after a backhand drop shot early in the second set and shrieked as she felt the full force of a back spasm.

After lengthy treatment, Williams continued but the power of her serve and groundstrokes were considerably diminished and 19-year-old Stephens took advantage in impressive fashion to run out a 3-6 7-5 6-4 winner in Rod Laver Arena.

Williams, who smashed her racket to pieces in frustration in the third set, tried graciously to honor the locker-room code that you do not diminish an opponent's achievement but was unable to wholly play down the significance of the injury.