Andy Murray beat Uzbekistan's Denis Istomin in the first New York night session of his US Open title defence to set up a quarter-final against Stanislas Wawrinka on Thursday.
The Briton was irritated by a number of bad line calls and struggled for consistency on a windy evening, but was not seriously threatened in a 6-7 (5-7) 6-1 6-4 6-4 win.
Murray, 26, was given prime-time billing on Arthur Ashe Stadium and duly delivered the expected victory to reach his 17th Grand Slam quarter-final.
However, it was hard going over three hours and seven minutes after he let a winning position slip in the first set, and it was 11.44pm local time (04:44 BST) by the time he punched away the winning volley.
He will next face ninth seed Wawrinka on Thursday after the Swiss upset fifth seed Tomas Berdych 3-6 6-1 7-6 (8-6) 6-2 on Louis Armstrong Stadium.