New York, USA: Wimbledon champions AndyMurray and Serena Williams again take center stage Wednesday, when the US Open semi-final lineup will be completed.
Murray, who followed up his third Grand Slam triumph at Wimbledon with Rio Olympics gold, takes on 2014 finalist Kei Nishikori for a place in the last four.
World number one Williams, gunning for a record seventh US Open title, faces fifth-seeded Romanian Simona Halep.
Williams, who has reached the quarter-finals without dropping her serve, has won seven of eight career matches against former French Open finalist Halep.
In addition to chasing a 23rd Grand Slam title -- which would carry her past the Open Era record she shares with Steffi Graf, Williams needs to at least reach the final to retain her world number one ranking now that second-seeded Angelique Kerber of Germany has booked her own semi-final berth.
Action kicks off on Arthur Ashe stadium at noon (1600 GMT) with 18-year-old Croatian Ana Konjuh taking on 10th-seeded Czech Karolina Pliskova in the first Grand Slam quarter-final for both.
Konjuh knocked off fourth-seeded Agnieszka Radwanska, avenging her heartbreaking loss to the Pole in the second round at Wimbledon, while Pliskova ousted Venus Williams to make the last eight of a Grand Slam for the first time after 17 prior attempts.
World number two Murray takes on Nishikori in an afternoon clash.
Murray will be hoping to extend an impressive record against Nishikori. He has won seven of eight previous meetings, most recently en route to Olympic gold in Rio last month.
"I played a really good match against him when we played a few weeks ago,"Murray said.
"I'm aware I'll need to do that again if I want to beat him, because he's one of the best players in the world."
The winner will face either Argentina's Juan Martin del Potro or Swiss third seed Stan Wawrinka.
Del Potro is back at the US Open after a three-year absence. At 142 in the world after a series of wrist injuries, the Argentine is the lowest-ranked player in 25 years to reach the quarters.
However, the 2009 US Open champion is playing well above that ranking, as evidenced by the silver medal in Rio that earned him a wild card invitation to the final Grand Slam of the year.
He promises to be a dangerous opponent for Wawrinka, a two-time semi-finalist who saved a match point en route to a third-round victory over Britain's Dan Evans before battling to a hard-fought four-set victory over Ukrainian Illya Marchenko in the round of 16.
"It's going to be a good challenge to play against him," Wawrinka said of del Potro.
"We played each other already this year at Wimbledon. He beat me. So it's going to be a good match again."