But the third-seeded Sharapova also double-faulted 10 times, a recurring theme ever since she returned from surgery on her right shoulder in 2008.
"I gave her too many free points," Sharapova said.
This has been a resurgent year for the Russian, who completed a career Grand Slam by winning the French Open in June, was the runner-up at the Australian Open and the Olympics, and briefly returned to No. 1 in the rankings — a spot that now belongs to Azarenka.
"I'll take the results I had this year," Sharapova said.
She reached her first U.S. Open semifinal since winning the 2006 title thanks to overcoming deficits en route to three-set victories in the fourth round and quarterfinals.
But she didn't have one more late-match charge in her.
With a cloudless blue sky and the temperature above 85 degrees, Arthur Ashe Stadium was steamy when Sharapova and Azarenka got started, shrieking loudly with nearly every stroke.
Well, Sharapova was ready at the outset, anyway. Azarenka? Not so much.
Sharapova took 12 of the first 17 points, hitting deep, clean groundstrokes, while Azarenka needed 18 minutes to win a single game. When they met in the Australian Open final, Sharapova won a total of three games. She equaled that by the time she led 3-0 when Friday's semifinal was 11 minutes old.
Azarenka, who came in averaging 20 winners per match in the tournament, managed to produce merely one in the first set. She finished with 19, the same number as her unforced error count. It was Sharapova whose play determined the result on most points: She had 44 winners and 42 unforced errors.
When Sharapova broke Azarenka to go ahead 1-0 in the second set, she appeared to be in control. But that's when Azarenka really showed up, taking four consecutive games and six of the next seven.
"All heart," said Azarenka, a 23-year-old from Belarus.
"That's what I feel like we play for, we live for," Azarenka said, "to play on these big stages against such champions."
She'll get a chance to do that again Saturday against Williams.
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