Defending champion Alexander Zverev outlasted Japan's Kei Nishikori 3-6, 6-1, 6-4 to reach the ATP Washington Open semi-finals while three-time Grand Slam champion Andy Murray withdrew citing fatigue.
Germany's third-ranked Zverev, seeking his fifth final of the season and third title of the year after Munich and Madrid, on Friday dispatched seventh-seed Nishikori, the 2015 champion, as he did in last year's Washington semi-finals.
"I felt like I had the more powerful shot," Zverev said.
"That worked out well in most of the rallies for me. It was a good high-level match."
Zverev booked a semi-final against 10th-seeded Greek 19-year-old Stefanos Tsitsipas, who eliminated Belgian third seed David Goffin 6-3, 6-4 in just 74 minutes.
"I'm super happy I got this win in two sets and saved some energy," Tsitsipas said.
"I was serving very well. Confidence plays a very important role in my game so getting early breaks was super important."
Australian Alex De Minaur, another 19-year-old, reached the semi-finals by walkover when Murray withdrew, citing the fatigue of three grueling three-set wins that kept him on the court more than eight hours in total.
Potro in Mifel final
lOS CABOS: Top-seeded Juan Martin del Potro of Argentina advanced to the Mifel Open final on Friday night, beating third-seeded Damir Dzumhur of Bosnia and Herzegovina 6-3, 7-6 (6).
Del Potro will face second-seeded Fabio Fognini of Italy, a 6-4, 6-2 winner over British left-hander Cameron Norrie in the first semifinal.
Sakkari ousts Venus
San Jose: Greece's Maria Sakkari delivered one of the biggest upsets of her career at the WTA San Jose tournament on Friday, ousting former seven-time Grand Slam champion Venus Williams in a straight sets shocker.
The 23-year-old Sakkari saved two set points in the second set en route to a 6-4, 7-6 (7/2) victory over the former world number one, punching her ticket to the semi-finals where she will face another unseeded player, Danielle Collins.
While, American Collins moved into the semi-finals after her opponent, former World No 1 Victoria Azarenka, retired midway through the second set due to a back injury.
Fourth-seeded Elise Mertens ended the giant-killing run of Konta to set up the other semi-final clash with Mihaela Buzarnescu.