US Open 2014: Caroline Wozniacki beats Maria Sharapova

Caroline Wozniacki was the 2009 US Open runner-up

Caroline Wozniacki thrilled the New York crowd with a stunning win over fifth seed Maria Sharapova at the US Open.

The Dane, seeded 10th, won 6-4 2-6 6-2 on a stiflingly hot afternoon at Flushing Meadows.

Wozniacki, 24, is through to her first Grand Slam quarter-final since 2012, and plays Italy's Sara Errani next.

"It means so much to me - it's been a bit up and down for me this year," said Wozniacki.

"It's a new year and I've gotten older, and hopefully a little wiser. I feel good. I feel comfortable when I play out there.

"The crowd was amazing today. It's just so much fun to play out there again on the big court."

Roared on by the majority of spectators on Arthur Ashe Stadium, the 2009 finalist looked back to her best as her superb defensive ability proved too much for Sharapova in a pulsating final set.

And she said that training to run the New York Marathon in November was aiding her game, adding: "I think it will help me a lot. Today was a tough battle out there. It was humid; it was hot; I had to change my dress.

"That rarely happens. It was just soaked. Definitely it's helping, because I felt fresh out there and I felt like I could keep going."

Wozniacki has slipped from the very top of the game after finishing as year-end world number one in 2010 and 2011, but in recent months there have been signs of a resurgence.

A title in Istanbul, a first top-five scalp in three years against Agnieszka Radwanska and twice taking Serena Williams to three sets suggested the Dane could again be a major threat, and beating Sharapova at a Grand Slam is confirmation of that.

The Dane made a terrific start, serving well and attacking the net as she moved 3-0 clear, but when Sharapova hauled her way back to 4-4 it seemed her heavier hitting would hold sway.

Sharapova has not been at her best in New York, however, and two wild forehand errors gave Wozniacki the first set.

It was hardly a crisis for the French Open champion, who leads the standings for three-set wins in 2014 with 17, and she dominated the second set with two breaks to level after nearly two hours.

With the temperature soaring, the heat rule was brought into effect and the players given a 10-minute break to leave the court.

Sharapova received a time violation on her return as umpire Marija Cicak said she had taken "way too much time", and early in the final set it was Wozniacki who complained that the Russian was too slow between serves.

Fired up and moving brilliantly behind the baseline, Wozniacki grabbed control of the match when she broke to love in a stunning rally at 2-1, chasing down everything Sharapova could throw at her until the Russian dumped a volley in the net.

The momentum was with the Dane and she would not flinch as her biggest win in recent memory loomed.

Attacking the Sharapova serve once more, Wozniacki stepped in and hammered a backhand winner to convert her first match point.

"I thought she played really well," said Sharapova. "She made me hit a lot of balls. That's always been her strength. But she did extremely well today.

"She's a great retriever, especially in these types of conditions. I just felt like I maybe went for a little too much."

Caroline Wozniacki's victory was only her third in eight matches against Maria Sharapova

Former world number one Wozniacki is bidding for her first grand slam title

Wozniacki had not been beyond the third round in the previous two US Opens