Top-ranked players Rafael Nadal and Karolina Pliskova advanced to the US Open quarter-finals with straight-sets victories on Monday.
Nadal reached the last eight for the seventh time by defeating Ukraine's 64th-ranked Alexandr Dolgopolov 6-2, 6-4, 6-1.
The 15-time grand slam champion, who had not made the US Open last eight since capturing the 2013 title, will next face the winner of a later match between Russian teen Andrey Rublev and Belgian ninth seed David Goffin.
The 31-year-old Spaniard, who claimed his 50th US Open match victory, returned to the top ranking last month for the first time since 2011.
"I played a solid match with not many mistakes," said Nadal, the reigning French Open champion.
"He's a player who can play amazing shots but sometimes he can be very unpredictable with errors so I just waited for my opportunity."
Meanwhile, Pliskova of the Czech Republic routed 91st-ranked American Jennifer Brady 6-1, 6-0 in just 46 minutes.
Pliskova, last year's US Open runner-up, will next face either 37th-ranked compatriot Lucie Safarova or US 20th seed CoCo Vandeweghe to decide a berth in the semi-finals.
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"It's very good for Czech tennis that there are so many of us," she said of the chance to play Safarova.
In her prior match, Pliskova faced a match point against China's Zhang Shuai, a tense moment that helped her ensure there was no drama against Brady.
"I played well," she said. "I really wanted to get the chance that I got after that match point. Definitely that match helped me to go through tough moments and this match I was much better."
The victory kept Pliskova in contention to retain her top ranking after the Open. She must reach the final to stay No 1.
