Novak Djokovic has not encountered any of the trouble he did in his previous match, eliminating qualifier Borna Gojo 6-2 7-5 6-4 to cruise through to the US Open quarter-finals.
Djokovic, who has won three of his men's record 23 grand slam titles at Flushing Meadows, needed to come back from a two-set deficit in the third round before eventually winning in five against fellow Serbian Laslo Djere.
On Sunday, Djokovic played far more cleanly and was in control throughout. He finished with 12 unforced errors, while his Croatian opponent made 40.
"Just glad to get through in straight sets," said the second-seeded Djokovic, who is assured of replacing Carlos Alcaraz at No.1 in the ATP rankings next week.
Djokovic won five of the big-serving Gojo's 15 service games while only getting broken once himself.
Next up for Djokovic will be a match-up against No.9 seed Taylor Fritz.
The 25-year-old from California set up the clash with a 7-6 (7-2) 6-4 6-4 win over Switzerland's Dominic Stricker and is the only player in the men's bracket to have not dropped a set so far.
"He has improved so much over the years," Djokovic said.
"The matches are only going to get tougher from now onwards. I'm ready."
Their meeting on Tuesday (Wednesday AEST) will be Djokovic's 13th quarter-final in New York and Fritz's first.
"I need to play within myself and trust that if I'm playing well, then that's going to be enough, and I don't need to do anything extra," Fritz said.
Djokovic is 7-0 against Fritz, one of three American men who won fourth-round matches, along with No.10 Frances Tiafoe and the unseeded Ben Shelton.
Shelton overcame another American, Tommy Paul, 6-4 6-3 4-6 6-4 on a steamy day in New York.
In a rematch of the pair's Australian Open quarter-final clash, Shelton avenged his four-set loss in Melbourne.
Tiafoe ended the US Open run to the last 16 of Australian wildcard Rinky Hijikata 6-4 6-1 6-4.
It is the first time a trio of men from the United States have made it to the quarter-finals at Flushing Meadows since 2005, when Andre Agassi, James Blake and Robby Ginepri did it.
"That's amazing for the (US Tennis Association), for the US Open as well," Djokovic said.
"All of the guys, Fritz, Shelton and Tiafoe, (use a) big serve, just very aggressive play."
The winner of Djokovic vs Fritz will take on the winner of Tiafoe vs Shelton in the semi-finals.