Second seed, Novak Djokovic reached the US Open semi-finals for the sixth consecutive year with a straight-sets win over Juan Martin del Potro.
The defending champion seed beat the Argentine 6-2 7-6 (7-3) 6-4 in a match more even than the scoreline suggests.
Djokovic, who has not lost a set in the tournament, was pushed hard before a second set lasting almost an hour and a half was settled on a tie-break.
Although the Serb was not at his best against an opponent whose power caused him considerable problems, Djokovic's superior athleticism and range of stroke eventually told.
A forehand down the line produced the error that brought him victory in three hours and six minutes - an hour and 20 minutes longer than he had been held up in any of the previous four rounds.
Del Potro was full of praise for Djokovic, saying: "He's playing better and better every match. He's the favourite to win."
The twenty five years old Serb will meet Spain's David Ferrer who fought back from 4-1 down in the fifth set to clinch a remarkable win over Serbia's Janko Tipsarevic and reach his second US Open semi-final.
The Spaniard secured a 6-3 6-7 (5-7) 2-6 6-3 7-6 (7-4) win in four hours and 31 minutes on Arthur Ashe Stadium.