NEW YORK -- Top-ranked American man John Isner had 30 aces in a 6-3, 6-4, 7-5, second-round victory over Hyeon Chung of South Korea.

The 10th-seeded Isner never lost his serve and fittingly hit his final ace on match point. He now has 52 aces in the tournament, more than any other player.

Isner next faces 23rd-seeded Mischa Zverev of Germany in the third round.