In Cincinnati’s ATP draw, Italy’s world number one Jannik Sinner beat Colombia’s Daniel Elahi Galan 6-1 6-1 in his first match since claiming his maiden Wimbledon title.
Taylor Fritz, who is number four in the men’s rankings, sent down 12 aces as he defeated qualifier and fellow American Emilio Nava 6-4 6-4.
However, eighth seed Lorenzo Musetti from Italy was bounced out by Benjamin Bonzi, with the Frenchman, ranked 63rd in the world, fighting back to win 5-7 6-4 7-6 (7-4).
Another Frenchman regrouped to pull off an upset as 70th-ranked Arthur Rinderknech beat Norway’s Casper Ruud, the 11th seed, 6-7 (5-7) 6-4 6-2.
The US Open, the final Grand Slam of the year, begins at Flushing Meadows, New York, on 24 August.