John Isner opened his bid for a fourth straight Atlanta Open title in style overpowering France's Adrian Mannarino 6-4 6-0.
Isner had 16 aces on the Atlantic Station hardcourt in the warm-up event for the US Open.
The top-seeded former University of Georgia star has reached the finals in Atlanta five of the previous six years and is 21-3 in the event.
In the quarter-finals, the 6-foot-10 American will face the winner of a late match between eighth-seeded Taylor Fritz and fellow American Bjorn Fratangelo.
Seventh-seeded Donald Young and fellow American Reilly Opelka set up a quarter-final match-up in the afternoon session.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Young beat countryman Tim Smyczek 4-6 7-6 (7-1) 6-3, and Opelka upset third-seeded South African Kevin Anderson 6-7 (7-5) 6-3 7-5.
Australia's Nick Kyrgios, who is the second seed at the event will get his tournament underway on Thursday (Friday AEST) when he takes on world No.123 American Jared Donaldson.
