Rafael Nadal and Juan Martin del Potro recorded contrasting wins on day seven of the US Open, while Dominic Thiem claimed the scalp of last year's runner-up, Kevin Anderson.
For the second match running in New York, Nadal was taken to four sets, but the top seed and defending champion ultimately proved too strong for Nikoloz Basilashvili.
Del Potro - the 2009 winner of the men's singles at Flushing Meadows - breezed past Borna Coric in the final match of the day.
The Argentinian will face home hope John Isner in the quarter-finals, while Thiem's reward for a straight-sets win over Anderson is a meeting with Nadal.
TOP-NOTCH THIEM EXPECTING TOUGH TEST FROM RAFA
While Nadal was below his brilliant best in a forgettable 6-3 6-3 6-7 (6-8) 6-4 win over the unseeded Basilashvili, Thiem produced arguably the performance of the day against Anderson.
The Austrian fired 42 winners and made only 13 unforced errors en route to a 7-5 6-2 7-6 (7-2) victory against the fifth seed.
Thiem has won three of his 10 meetings with Nadal, all of those contests taking place on clay, but rejected the idea his game "matches up well" with the world number one.
"I think nobody's game really matches up well with his," said Thiem, who turns 25 on Monday. "That's why he's so unbelievably successful. No matter what, it's always really tough to play against him."
EASY EVENING FOR DELPO
World number three Del Potro has never lost in the fourth round of the US Open and that streak was maintained with ease against an agitated Coric.
Del Potro seized control by breaking to win the 10th game and never looked likely to relinquish his grip on the contest, particularly after Coric received treatment on an apparent hamstring problem late in the second set.
A 6-4 6-3 6-1 triumph was wrapped up in two hours and four minutes, to the delight of a group of enthusiastic Argentine fans on Arthur Ashe.
IN-FORM ISNER FEELS BETTER THAN EVER
Isner came through a five-setter with Milos Raonic, who was hampered by a "sharp feeling" in his hip during the closing stages of the match.
A quarter-finalist in New York seven years ago, Isner was asked to compare his game then and now.
"I think I'm better," replied the experienced American, who made his first grand slam semi-final at Wimbledon in July.
"Physically I'm stronger, wiser, I have a lot of experience on my side. I'm feeling really good. Just in a good place, happy.
"I'm really enjoying competing, not putting too much pressure on myself. To do that at 33 now is pretty cool."