Maria Sharapova was knocked out of the US Open by Caroline Wozniacki on Sunday, leaving the women's draw with just two of its top eight seeds while Roger Federer made the most of heavy rain to make the last-16. (Related: HowÂ counterintuitive Wozniacki upset Sharapova)
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.
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.
Five-time champion Federer sat out a two-hour break for torrential rain to race into the fourth round.
The second-seeded Swiss, the champion between 2004-2008, came back from a set down to defeat Spain's Marcel Granollers 4-6, 6-1, 6-1, 6-1 by racing away with 20 of the last 24 games of the match which had been interrupted due to rain and the threat of lightning.
Federer, bidding to become the oldest Grand Slam champion in more than 40 years, clinched his 70th win at the tournament on the back of 57 winners and 13 aces.
But the 33-year-old had struggled in the first set where he slipped to 2-5 down against the world number 42 before he grasped welcome respite in the locker room to sit out the storm.
- Humid conditions -
"It was a good match and I managed to turn it around as Marcel was on fire at the start," said Federer.
"The break helped me and when I came back I played some great tennis. The conditions were windy and quick at the start but when we got back it was humid and that played in my favour."
Federer will face Roberto Bautista Agut for a place in the quarter-finals after the 26-year-old Spaniard beat France's Adrian Mannarino 7-5, 6-2, 6-3.
Gilles Simon sent Spanish fourth seed David Ferrer crashing to his earliest US Open defeat in five years with a 6-3, 3-6, 6-1, 6-3 third round win.
The 26th seeded Simon capitalised on the 52 unforced errors of the 32-year-old Ferrer, a semi-finalist in 2007 and 2012, who appeared to struggle physically towards the end.
Simon goes on to face Marin Cilic of Croatia, who beat South Africa's Kevin Anderson 6-3, 3-6, 6-3, 6-4, for a place in the quarter-finals in a clash of two men who both missed the 2013 tournament.
Simon was back in France for the birth of his second child while Cilic was serving out a doping ban.
Czech sixth seed Tomas Berdych, a semi-finalist in 2012, beat Georgian-born Russian Teymuraz Gabashvili 6-3, 6-2, 6-4 and next plays Dominic Thiem of Austria, the youngest player in the top 50 at just 20.
Thiem, who turns 21 on Wednesday, reached his first Grand Slam last-16 with an impressive 6-4, 6-2, 6-3 win over left-handed serve-and-volleyer Feliciano Lopez of Spain who is 12 years his senior.