The American teenager outlasted the former Australian Open ladies champion in one quarterfinal match. Meanwhile, Roger Federer will play Andy Murray in the men's semifinals.
Serena Williams went down smashing rackets and screaming as she bowed out of the Australian Open quarterfinals 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-time 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."