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."
Kuznetsova lost confidence in the face of Sharapova's fightback. Her groundstrokes disintegrated and she failed to hold serve in the last two sets, surrendering eight straight service games to slip to defeat in 137 minutes.
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.