Rafael Nadal powered past Chung Hyeon into the US Open fourth round, capitalising on the extra rest he enjoyed before facing the South Korean.
The Spanish second seed, who had a walkover in the previous round, had not played since Tuesday and it showed in a dominant 6-3 6-4 6-2 win.
By contrast, Chung had come through three rounds of qualifying and spent nine hours more on court.
Nadal faces Marin Cilic next, while sixth seed Alexander Zverev also won.
Australian 28th seed Nick Kyrgios failed in his bid to progress past the third round at Flushing Meadows for the first time after losing 7-6 (7-5) 7-6 (7-5) 6-3 to Russian Andrey Rublev.