Wimbledon champion Maria Sharapova fought back from a sloppy start to wear down fellow Russian Svetlana Kuznetsova 4-6, 6-2, 6-2 on Tuesday to reach the Australian Open semi-finals for the first time.
Fourth seed Sharapova was tentative and error-prone in the first set and was out-hit by the aggressive U.S. Open champion Kuznetsova, 19, who used pace and depth from the back of the court.
The 17-year-old then staged a remarkable comeback after losing her serve to fifth seed Kuznetsova in the first game of the second set.
Sharaprova rallied as her opponent's game wilted on a scorching hot Rod Laver Arena where the temperature reached 33 degrees Celsius (91 degrees Fahrenheit).
"I need a wheelchair right now," Sharapova said in a television interview after her victory.
"Mentally I just tried to tough it out. I thought this was one of the toughest matches of my life."
A dispirited Kuznetsova was 40-15 up in her final service game but lamely handed Sharapova her first match point with a double fault.
Sharapova clinched victory following a desperate rally, lunging across the baseline to whip a forehand cross court past a stranded Kuznetsova.
She now plays seventh seed and 2003 champion Serena Williams or second seed and 1999 runner-up Amelie Mauresmo in the semi-finals.
The start of Kuznetsova's Open campaign was overshadowed by a doping row when a Belgian government minister said she had tested positive for ephedrine, a stimulant commonly found in cough medicines, at an exhibition tournament last month.
But outraged tennis officials defended Kuznetsova, saying ephedrine was not banned at "out of competition" exhibition events.