Rafael Nadal has moved ominously into the last 16 at the US Open with a straight-sets win over Chung Hyeon in Arthur Ashe Stadium.

The Spanish second seed made light work of South Korean qualifier Chung, winning their third-round match 6-3 6-4 6-2 in just under two hours on Saturday.

With fitness doubts hanging over defending champion and world No.1 Novak Djokovic, and third seed Roger Federer looking susceptible in his earlier rounds, Nadal must sense a huge opportunity to add to his three titles at Flushing Meadows.

The draw has certainly been kind to him with both his great rivals on the other side, while second-round opponent, Australia’s Thanasi Kokkinakis, was forced to withdraw through injury.

Nadal had spent just two hours on court beforer Saturday and he has dispensed with the tape he usually has strapped around his knees, which have given him so many injury troubles in the past.

“The tape is not working any more,” he said.

“But I’m happy to be playing on the hard court. I’m trying to play a bit more aggressive. I’m happy to be in the fourth round one more time.

“Last year I had some tough matches and in the semi-final I had to retire. This year I had to miss some tournaments, I’m not 25 anymore.

“You never know what’s better or worse, all that matters to me is I’m in the fourth round.

“I just think day by day, try to practice and be ready for a tough match.”

Nadal will face Marin Cilic next after the Croatian overcame American 14th seed John Isner 7-5 3-6 7-6 (8-6) 6-4.

Cilic, the 22nd seed and 2014 champion in New York, mixed 21 aces with an astonishing 17 double faults but Isner could only break serve once from 14 opportunities.

Conversely Isner served 40 aces but was broken twice in the match.

On Louis Armstrong Stadium, German Alexander Zverev toughed out a 6-7 (4-7) 7-6 (7-4) 6-3, 7-6 (7-3) victory over Slovenian Aljaz Bedene.

The sixth-seeded Zverev slammed 25 aces as he took more than three-and-a-half hours to beat his 80th-ranked opponent .

Zverev will meet Argentine Diego Schwartzman or American Tennys Sandgren in the fourth round chasing a first US Open quarter-final appearance.

Earlier in the day, Pablo Andujar beat Alexander Bublik of Kazakhstan 6-4 6-3 6-2 with the unseeded Spaniard to face France’s Gael Monfils or Canada’s Denis Shapovalov in the next round.