Maria Sharapova's 10th US Open ended in defeat to fellow former world number one Caroline Wozniacki, leaving the women's draw with just two of its top eight seeds.
Also exiting on an afternoon of high humidity, which eventually descended into an early evening of lightning and torrential rain, was Spanish fourth seed David Ferrer, the highest-ranked casualty in the men's event.
Five-time Grand Slam champion Sharapova -- the 2006 title winner in New York -- was defeated by Danish 10th seed Wozniacki with the 2009 runner-up claiming a deserved 6-4, 2-6, 6-2 triumph on a steamy Arthur Ashe Stadium court to reach the quarter-finals yesterday.
Sharapova, looking to add this year's US Open title to her French Open win in June, was undone by 43 unforced errors and eight double faults.
The hot and humid conditions were so punishing that the players were granted a heat break in the locker room before the third set, and when they returned to the court Wozniacki wasted little time, breaking Sharapova to love in the fourth game for a 3-1 lead.
She broke the Russian superstar again in the final game to seal the victory and a chance to play 13th-seeded Italian Sara Errani for a semi-final berth.
Errani ended the magical run of 32-year-old Croatian qualifier Mirjana Lucic-Baroni 6-3, 2-6, 6-0.
"It means so much to me," said Wozniacki, who reached the semi-finals in 2010 and 2011 but hadn't been past the third round at Flushing Meadows the last two years.
"It's been a bit up and down for me this season," she added. "To win today against a champion like Maria is an unbelievable feeling."
The departure of fifth-seeded Sharapova leaves just two of the women's top eight left -- world number one and two-time defending champion Serena Williams and seventh-seeded Canadian Eugenie Bouchard.
"I thought she played really well. 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," said Sharapova.
