Second-seeded Rafael Nadal looked dominant in his first-round U.S. Open match, easily defeating Australian John Millman 6-3, 6-2, 6-2.

Nadal, who is undefeated in U.S. Open first rounds, may have had reason to worry about Millman, who upset Roger Federer last year in the fourth round at Flushing Meadows. But the 60th-ranked Australian could not compete with Nadal from the baseline. The Spaniard capped his workmanlike victory with a clean forehand winner.

Next up for Nadal is another Australian, Thanasi Kokkinakis, a wild-card entry ranked 203rd.

Fourth-seeded Dominic Thiem is out at the U.S. Open.

The French Open finalist fell to 87th-ranked Italian Thomas Fabbiano 6-4, 3-6, 6-3, 6-2, becoming the second young hopeful on the men's side to go down in a matter of hours. Eighth-seeded Stefanos Tsitsipas earlier fell to Russian Andrey Rublev 6-4, 6-7 (5), 7-6 (7), 7-5.

Fabbiano is no stranger to such upsets, having stunned Tsitsipas at Wimbledon this year and Stan Wawrinka at Wimbledon last year. But Fabbiano has never advanced beyond the third round of a Grand Slam tournament.