Sharapova of Russia celebrates defeating Azarenka of Belarus in their women's singles semi-final match at the French Open tennis tournament in Paris (Photo: Reuters)
The Russian, who next meets world number one Serena Williams or fifth-seeded Italian Sara Errani, served 12 aces and 11 double faults in a see-saw encounter against the Belarussian.
Second seed Sharapova raced through the opening set in less than half an hour, spraying Court Philippe Chatrier with forehand winners.
Double Australian Open champion Azarenka hit back to take the second set but lost her momentum after a 30-minute rain interruption, her opponent wrapping it up on her fifth match point after two hours 10 minutes of baseline biffing and shrieking.
Four-times grand slam champion Sharapova will need to make a dramatic improvement to become the first female to retain her title on the Paris clay since Belgium's Justine Henin in 2007.
The Russian thumped 42 winners, most of them with her devastating forehand, but a total of 39 unforced errors also meant the contest could have gone either way.
Sharapova, who lost the opening set 6-0 to Serb Jelena Jankovic in the quarter-finals, made two double faults as she dropped her serve in the first game against Azarenka.
The Belarussian was making her first appearance in the French Open semi-finals but she also needed time to settle.
By the time she realised that, Sharapova had won six games in a row in 28 minutes, allowing the third seed only seven points in the process.
Dark clouds
Azarenka started to find better angles in the second set and opened a 40-15 lead in the third game before a couple of sharp first-service return winners reminded her she would have to fight for every point.
Dark clouds gathered in the sky as Azarenka broke to go 4-2 up when Sharapova netted a backhand.
The Russian poster girl then conceded two break points at 5-2 when the umpire called Azarenka's shot in although TV footage showed the ball was long.
Sharapova saved the first break point with an ace but double faulted on the second.
The rain then intervened and it seemed to take the wind out of Azarenka's sails.
"I think the break kind of changed the momentum," she told a news conference. "I was just trying to make things happen too quick and started missing the ball."
A backhand winner gave Sharapova a break for 2-1, only for Azarenka to break back after yet another double fault at the end of a 10-minute game.
Sharapova kept playing at a hectic pace and soon went 5-2 ahead.
Azarenka saved four match points as she broke back for 5-3 and then held serve but the title holder already had her teeth sunk deep into her prey and finished the match off with an ace.
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