Top seed John Isner booked his spot in the quarter-finals of the Citi Open after taking down 15th seed Marcos Baghdatis 7-6 (3), 6-2 on Thursday.
Isner is looking to bounce back after failing to impress at Wimbledon, where he lost to Jo-Wilfried Tsonga in the third round.
Isner will face Steve Johnson in the last eight after the fifth seed defeated American compatriot Ryan Harrison 6-4, 6-4.
Second seed Gael Monfils, fourth seed Benoit Paire, sixth seed Jack Sock, seventh seed Alexander Zverev and eighth seed Sam Querrey also progressed to the quarter-finals after they triumphed over Borna Coric, Gilles Muller, Daniel Evans, Malek Jaziri and Alexandr Dolgopolov respectively.
There was one major upset on Thursday though as third seed Bernard Tomic lost to 13th seed Ivo Karlovic 6-7 (7), 3-6.