Stephens bounces Serena in quarters

Novak Djokovic celebrates winning a point during his Australian Open final victory over Andy Murray.
Novak Djokovic celebrates winning a point during his Australian Open final victory over Andy Murray.
Belarusian Victoria Azarenka kisses the Daphne Akhurst Memorial Cup in the locker room as women's singles champion.
Belarusian Victoria Azarenka kisses the Daphne Akhurst Memorial Cup in the locker room as women's singles champion.
Victoria Azarenka bursts into tears after defeating Li Na for back-to-back Australian Open titles.
Victoria Azarenka bursts into tears after defeating Li Na for back-to-back Australian Open titles.
China's Li Na grimaces after injuring her left ankle during the Australian Open women's final.
China's Li Na grimaces after injuring her left ankle during the Australian Open women's final.
Andy Murray missed a chance to serve out the match in the fourth set, but finished off Roger Federer in the fifth.
Andy Murray missed a chance to serve out the match in the fourth set, but finished off Roger Federer in the fifth.
A dejected Roger Federer during his post-match press conference.
A dejected Roger Federer during his post-match press conference.
Novak Djokovic of Serbia hits a return to David Ferrer of Spain.
Novak Djokovic of Serbia hits a return to David Ferrer of Spain.
David Ferrer of Spain reacts during his men's singles semi-final match against Novak Djokovic of Serbia.
David Ferrer of Spain reacts during his men's singles semi-final match against Novak Djokovic of Serbia.
Sloane Stephens of the United States of America plays a backhand in her Semifinal match against Victoria Azarenka of Belarus.
Sloane Stephens of the United States of America plays a backhand in her Semifinal match against Victoria Azarenka of Belarus.
Victoria Azarenka of Belarus plays a backhand in her Semifinal match against Sloane Stephens of the United States.
Victoria Azarenka of Belarus plays a backhand in her Semifinal match against Sloane Stephens of the United States.
Li Na swept Maria Sharapova aside 6-2 6-2 in the first semifinal at the Australian Open.
Li Na swept Maria Sharapova aside 6-2 6-2 in the first semifinal at the Australian Open.
It was not Maria Sharapova's day, winning just four games in a straight sets loss to Li Na.
It was not Maria Sharapova's day, winning just four games in a straight sets loss to Li Na.
 Roger Federer of Switzerland plays a backhand in his Quarterfinal match against Jo-Wilfred Tsonga.
Roger Federer of Switzerland plays a backhand in his Quarterfinal match against Jo-Wilfred Tsonga.
Jo-Wilfred Tsonga of France reacts in his Quarterfinal match against Roger Federer.
Jo-Wilfred Tsonga of France reacts in his Quarterfinal match against Roger Federer.
Andy Murray celebrates his win over Jeremy Chardy.
Andy Murray celebrates his win over Jeremy Chardy.
Andy Murray during his match against Jeremy Chardy.
Andy Murray during his match against Jeremy Chardy.
Sloane Stephens of the US (R) shakes hands with compatriot Serena Williams after defeating her in their women's singles quarter-final match.
Sloane Stephens of the US (R) shakes hands with compatriot Serena Williams after defeating her in their women's singles quarter-final match.
Serena Williams does the splits during her quarterfinals loss to compatriot Sloane Stephens.
Serena Williams does the splits during her quarterfinals loss to compatriot Sloane Stephens.
Victoria Azarenka of Belarus celebrates winning her Quarterfinal match against Svetlana Kuznetsova.
Victoria Azarenka of Belarus celebrates winning her Quarterfinal match against Svetlana Kuznetsova.
Svetlana Kuznetsova of Russia looks on after falling in her Quarterfinal match against Victoria Azarenka.
Svetlana Kuznetsova of Russia looks on after falling in her Quarterfinal match against Victoria Azarenka.
Maria Sharapova of Russia celebrates defeating Ekaterina Makarova.
Maria Sharapova of Russia celebrates defeating Ekaterina Makarova.
Ekaterina Makarova of Russia plays a backhand in her Quarterfinal match against Maria Sharapova.
Ekaterina Makarova of Russia plays a backhand in her Quarterfinal match against Maria Sharapova.
Maria Sharapova of Russia hits a return to compatriot Ekaterina Makarova.
Maria Sharapova of Russia hits a return to compatriot Ekaterina Makarova.
David Ferrer of Spain reacts during his men's singles quarter-final match against compatriot Nicolas Almagro.
David Ferrer of Spain reacts during his men's singles quarter-final match against compatriot Nicolas Almagro.
Li Na celebrates her win over fourth-seeded Agnieszka Radwanska.
Li Na celebrates her win over fourth-seeded Agnieszka Radwanska.
Roger Federer of Switzerland celebrates winning the second set during his men's singles match against Milos Raonic.
Roger Federer of Switzerland celebrates winning the second set during his men's singles match against Milos Raonic.
Andy Murray signs autographs after his fourth round victory over Frenchman Gilles Simon.
Andy Murray signs autographs after his fourth round victory over Frenchman Gilles Simon.
Roger Federer of Switzerland serves to Milos Raonic of Canada.
Roger Federer of Switzerland serves to Milos Raonic of Canada.
Serena Williams of the US serves to Maria Kirilenko of Russia.
Serena Williams of the US serves to Maria Kirilenko of Russia.
Andy Murray of Britain celebrates defeating Gilles Simon of France.
Andy Murray of Britain celebrates defeating Gilles Simon of France.
Victoria Azarenka of Belarus (right) kisses Elena Vesnina of Russia after defeating her in their women's singles match at the Australian Open.
Victoria Azarenka of Belarus (right) kisses Elena Vesnina of Russia after defeating her in their women's singles match at the Australian Open.
Novak Djokovic celebrates after his five-hour, two-minute five-set victory over Stanislas Wawrinka in the fourth round at the Australian Open.
Novak Djokovic celebrates after his five-hour, two-minute five-set victory over Stanislas Wawrinka in the fourth round at the Australian Open.
Ana Ivanovic is certain she is in good form despite exiting yet another major before the quarter-finals.
Ana Ivanovic is certain she is in good form despite exiting yet another major before the quarter-finals.
Maria Sharapova has lost just five games in her four wins at this year's Australian Open.
Maria Sharapova has lost just five games in her four wins at this year's Australian Open.
Agnieszka Radwanska of Poland celebrates defeating Ana Ivanovic of Serbia during their women's singles match at the Australian Open.
Agnieszka Radwanska of Poland celebrates defeating Ana Ivanovic of Serbia during their women's singles match at the Australian Open.
Maria Sharapova of Russia hits a return to Kirsten Flipkens of Belgium.
Maria Sharapova of Russia hits a return to Kirsten Flipkens of Belgium.
David Ferrer of Spain serves to Kei Nishikori of Japan during their men's singles match at the Australian Open.
David Ferrer of Spain serves to Kei Nishikori of Japan during their men's singles match at the Australian Open.
David Ferrer of of Spain plays a forehand in his fourth round match against Kei Nishikori.
David Ferrer of of Spain plays a forehand in his fourth round match against Kei Nishikori.
 Maria Sharapova (right) of Russia after her fourth round match against Kirsten Flipkens.
Maria Sharapova (right) of Russia after her fourth round match against Kirsten Flipkens.
Angelique Kerber of Germany receives medical treatment during her women's singles match against Ekaterina Makarova.
Angelique Kerber of Germany receives medical treatment during her women's singles match against Ekaterina Makarova.
Ekaterina Makarova of Russia hits a return to Angelique Kerber of Germany during their women's singles match at the Australian Open.
Ekaterina Makarova of Russia hits a return to Angelique Kerber of Germany during their women's singles match at the Australian Open.
Gael Monfils is doubled over with exhaustion during his epic third round match against Gilles Simon.
Gael Monfils is doubled over with exhaustion during his epic third round match against Gilles Simon.
Bernard Tomic and Roger Federer share a pat on the back after their third round match.
Bernard Tomic and Roger Federer share a pat on the back after their third round match.
Caroline Wozniacki returns a shot during her third round win.
Caroline Wozniacki returns a shot during her third round win.
Serena and Venus Williams whisper tactics during their second round doubles match.
Serena and Venus Williams whisper tactics during their second round doubles match.
Frenchman, world number 36, Michael Chardy lines up the ball in his Australia Open third round victory over sixth-seed Juan Martin del Potro.
Frenchman, world number 36, Michael Chardy lines up the ball in his Australia Open third round victory over sixth-seed Juan Martin del Potro.
Andy Murray exclaims his satisfaction at beating Ricardas Berankis of Lithuania in the third round of the Australian Open.
Andy Murray exclaims his satisfaction at beating Ricardas Berankis of Lithuania in the third round of the Australian Open.
Victoria Azarenka hits a return to Jamie Hampton.
Victoria Azarenka hits a return to Jamie Hampton.
Jamie Hampton celebrates winning the second set during her women's singles match against Victoria Azarenka.
Jamie Hampton celebrates winning the second set during her women's singles match against Victoria Azarenka.
Novak Djokovic is at full strength during his win over Radek Stepanek.
Novak Djokovic is at full strength during his win over Radek Stepanek.
Maria Sharapova celebrates her 6-1, 6-3 victory over Venus Williams.
Maria Sharapova celebrates her 6-1, 6-3 victory over Venus Williams.
Ana Ivanovic pumps her fist after beating fellow Serbian Jelena Jankovic.
Ana Ivanovic pumps her fist after beating fellow Serbian Jelena Jankovic.
Tomas Berdych returns a shot during his match against Jurgen Melzer.
Tomas Berdych returns a shot during his match against Jurgen Melzer.
 Agnieszka Radwanska of Poland plays a forehand in her third round match against Heather Watson of Great Britain.
Agnieszka Radwanska of Poland plays a forehand in her third round match against Heather Watson of Great Britain.
Angelique Kerber of Germany hits a return to Madison Keys of the US.
Angelique Kerber of Germany hits a return to Madison Keys of the US.
Stefan 'Redfoo' Gordy of the American electro duo LMFAO attends the MLC Hotshots session at the Australian Open.
Stefan 'Redfoo' Gordy of the American electro duo LMFAO attends the MLC Hotshots session at the Australian Open.
The pink and black shoes of Roger Federer.
The pink and black shoes of Roger Federer.
Roger Federer picked up early breaks in each set to defeat Nikolay Davydenko in straight sets in Melbourne.
Roger Federer picked up early breaks in each set to defeat Nikolay Davydenko in straight sets in Melbourne.
Bernard Tomic recovered from losing a first set tie-breaker to defeat German qualifier Daniel Brands in four sets.
Bernard Tomic recovered from losing a first set tie-breaker to defeat German qualifier Daniel Brands in four sets.
Andy Murray plays a forehand in his second round match against Joao Sousa of Portugal during day four of the 2013 Australian Open
Andy Murray plays a forehand in his second round match against Joao Sousa of Portugal during day four of the 2013 Australian Open
Serena Williams of the United States of America plays a backhand in her second round match against Garbine Muguruza of Spain.
Serena Williams of the United States of America plays a backhand in her second round match against Garbine Muguruza of Spain.
Jo-Wilfried Tsonga plays a backhand in his second round match against Go Soeda of Japan.
Jo-Wilfried Tsonga plays a backhand in his second round match against Go Soeda of Japan.
Victoria Azarenka of Belarus plays a backhand in her second round match against Eleni Daniilidou of Greece.
Victoria Azarenka of Belarus plays a backhand in her second round match against Eleni Daniilidou of Greece.
Novak Djokovic lost just six games as he cruised to a straight sets victory over American Ryan Harrison.
Novak Djokovic lost just six games as he cruised to a straight sets victory over American Ryan Harrison.
Heather Watson of Great Britain celebrates with fans after her second round singles win.
Heather Watson of Great Britain celebrates with fans after her second round singles win.
Maria Sharapova waits for a serve from Japan's Misaki Doi during her second round roll-over.
Maria Sharapova waits for a serve from Japan's Misaki Doi during her second round roll-over.
Bob and Mike Bryan perform their trademark chest bump after winning their opening doubles match.
Bob and Mike Bryan perform their trademark chest bump after winning their opening doubles match.
Sam Stosur exits Rod Laver Arena after her second round defeat to China's Zheng Jie
Sam Stosur exits Rod Laver Arena after her second round defeat to China's Zheng Jie
Tomas Berdych of the Czech Republic plays a backhand in his second round match against Guillaume Rufin of France.
Tomas Berdych of the Czech Republic plays a backhand in his second round match against Guillaume Rufin of France.
Jerzy Janowicz exploded in rage after losing a 79-minute set to India’s Somdev Devvarman.
Jerzy Janowicz exploded in rage after losing a 79-minute set to India’s Somdev Devvarman.
Kei Nishikori of Japan plays a backhand in his second round match against Carlos Berlocq of Argentina.
Kei Nishikori of Japan plays a backhand in his second round match against Carlos Berlocq of Argentina.
Daniel Gimeno-Traver of Spain hits a return to compatriot Nicolas Almagro during their men's singles match at the Australian Open.
Daniel Gimeno-Traver of Spain hits a return to compatriot Nicolas Almagro during their men's singles match at the Australian Open.
Agnieszka Radwanska of Poland hits a return to Irina-Camelia Begu of Romania.
Agnieszka Radwanska of Poland hits a return to Irina-Camelia Begu of Romania.
Jarmila Gajdosova of Australia does the splits in her first round match against Yanina Wickmayer.
Jarmila Gajdosova of Australia does the splits in her first round match against Yanina Wickmayer.
Gael Monfils celebrates a point during his first round match.
Gael Monfils celebrates a point during his first round match.
Fans scramble for signatures from Argentinian Juan Martin del Potro.
Fans scramble for signatures from Argentinian Juan Martin del Potro.
No 1 seed Victoria Azarenka in action on day two.
No 1 seed Victoria Azarenka in action on day two.
Melbourne Park is lit up for the night session on day two.
Melbourne Park is lit up for the night session on day two.
Bernard Tomic keeps his eye on the ball.
Bernard Tomic keeps his eye on the ball.
Andy Murray returns a shot against Robin Haase on day two of the Australian Open.
Andy Murray returns a shot against Robin Haase on day two of the Australian Open.
Caroline Wozniacki in action during her first round match against Sabine Lisicki.
Caroline Wozniacki in action during her first round match against Sabine Lisicki.
Novak Djokovic on his way to a first round straight sets victory.
Novak Djokovic on his way to a first round straight sets victory.
Maria Sharapova serves during her first round win.
Maria Sharapova serves during her first round win.
A packed house shows up to watch local Lleyton Hewitt's first round match at Rod Laver Arena.
A packed house shows up to watch local Lleyton Hewitt's first round match at Rod Laver Arena.
Ana Ivanovic celebrates a point during her match against Melinda Czink.
Ana Ivanovic celebrates a point during her match against Melinda Czink.
Janko Tipsarevic celebrates his straight sets win over Lleyton Hewitt in the first round.
Janko Tipsarevic celebrates his straight sets win over Lleyton Hewitt in the first round.
David Ferrer lies on court after throwing himself at a point during his first round win over Olivier Rochus.
David Ferrer lies on court after throwing himself at a point during his first round win over Olivier Rochus.
Fan show their home town support on day one.
Fan show their home town support on day one.
Lleyton Hewitt's returns a point during his loss to Janko Tipsarevic.
Lleyton Hewitt's returns a point during his loss to Janko Tipsarevic.

American teenager Sloane Stephens caused the biggest upset at this year's Australian Open when the 29th seed rallied to overcome an injury-hampered Serena Williams in the quarter-finals this evening.

Stephens prevailed 3-6 7-5 6-4 to set up a semi-final against world number one Victoria Azarenka, the 19-year-old maintaining her focus to see out the victory after the five-time champion had jarred her back in the second set and left the court for medical treatment.

''Oh my goodness,'' an emotional Stephens said in a courtside interview as she secured a maiden grand slam semi-final berth. ''I'm sure my grandparents are freaking out. I'm sure they're watching on the computer.''

The match was billed as a showdown pitting the future of American tennis against the most accomplished player of the present generation, and the early signs indicated that Williams possessed too much power for her younger opponent.

Both players hammered away at each other on serve in the opener with the receiver winning a total of two points until the eighth game, when Williams broke Stephens to take a 5-3 lead then held to seal the set in 28 minutes.

The nature of the contest changed dramatically when Williams, already concerned by an ankle injury sustained in the first round, appeared to twinge her back when chasing a drop shot in the eighth game of the second set.

Visibly in pain, the 31-year-old's vigour disappeared and she took a medical timeout to have the injury assessed. Tournament officials told ESPN that she was suffering from spasms.

MENTAL BLOCK

The 15-times grand slam champion, who had looked in such distress that it appeared she would retire from the match, somehow returned but there was no zip to her serve.

Averaging more than 170kph throughout the tournament and with several serves in excess of 200kph, the American was barely able to roll her shoulder over, with the sole aim of getting the ball into the service box to begin rallies.

By contrast, Stephens, appeared to suffer a mental block,  getting broken when she was serving for the set while Williams, who was now serving less than 130kph, held to love as the slower paced deliveries affected the teenager's timing.

Stephens, however, managed to regain her composure and win the next two games to take the set 7-5 and level the match.

Frustrated and in pain, Williams let her anger boil over at the end of the third game of the decider after Stephens had taken a 2-1 lead.

Williams twice smashed her racquet into the court and hurled the broken equipment under her chair and the momentary outburst of destruction appeared to work in her favour as she cranked up the speed of her serve again.

Looking more comfortable in her movement, Williams broke to make it 4-3 in the decider but was unable to prevent her gutsy opponent from breaking back immediately.

Stephens then held and broke again to seal the shock victory and set up a semi-final against defending champion Azarenka after the Belarusian had beaten Svetlana Kuznetsova 7-5 6-1 in the early match on Rod Laver Arena.

Reuters