Roland Garros runner-up Robin Soderling became the first man to reach the quarter-finals of the US Open on Monday when his eighth-seeded opponent Nikolay Davydenko retired with a leg injury.
Russian Davydenko hobbled around court with his left leg heavily strapped but after losing the third set, he shook his head and informed the umpire he could not continue.
The retirement would also have been a relief for Soderling, who had suffered a dizzy spell during the 7-5, 3-6, 6-2 win.
The Swedish 12th seed's victory also set the stage for a possible rematch with Roger Federer, the only man to have beaten Soderling in the last two Grand Slam events.
French Open and Wimbledon champion Federer faces Spaniard Tommy Robredo later on Monday.
Kateryna Bondarenko in her first Grand Slam singles QFl
Kateryna Bondarenko reached her first Grand Slam singles quarter-final, annihilating Argentina's Gisela Dulko 6-0, 6-0 in the fourth round.
Late arrivals on Arthur Ashe would have missed the Ukrainian's 47-minute breeze against an error-strewn opponent who knocked out her seeded older sister Alona in round two.
"I just got some messages to do the revenge for my sister, so I start to think about it when I read the messages," Bondarenko told reporters.
"I'm surprised that it's 6-0, 6-0, and I'm really happy that it went that way."
With no seeds left in the top quarter of the draw, Bondarenko has a golden chance to reach the semi-finals of what has been an unpredictable tournament.
She faces a last eight test against Petra Kvitova, conqueror of top seed Dinara Safina, or Yanina Wickmayer of Belgium.
