Defending champ Alexander Zverev edges Kei Nishikori in D.C. quarterfinal; Andy Murray out

WASHINGTON – Defending champion Alexander Zverev returned to the Citi Open semifinals by coming back for a 3-6, 6-1, 6-4 victory over No. 7 seed Kei Nishikori at the rain-drenched tournament Friday.

Only two other men’s and women’s quarterfinals were completed before all play was called off on a wet day that also included three-time major champion Andy Murray’s withdrawal.

The No. 1-seeded Zverev, who beat his older brother, Mischa, in the third round, also eliminated 2015 Washington champion Nishikori at the hard-court tuneup for the U.S. Open a year ago en route to the title.

Germany’s Zverev, 21, improved to 14-2 in his four appearances at the Citi Open.

On Saturday, he’ll face 19-year-old Stefanos Tsitsipas of Greece. The No. 10 seed Tsitsipas beat No. 3 David Goffin 6-3, 6-4.

Tsitsipas is coming off his first run to the fourth round at a Grand Slam tournament, last month at Wimbledon.

On the other half of the draw, Murray pulled out of his quarterfinal after winning a trio of three-setters and lamenting a schedule that had him start his latest victory at midnight.

Murray cited fatigue when he withdrew Friday, hours before he was supposed to face 19-year-old Alex de Minaur, who was given a walkover into the semifinals. The remaining men’s quarterfinal between No. 16 Andrey Rublev of Russia and unseeded Denis Kudla, who is from nearby Arlington, Virginia, never got started because of rain and was pushed to Saturday.

In the only women’s quarterfinal that concluded, Andrea Petkovic got past No. 6 seed Belinda Bencic 6-3, 2-6, 7-6 (8). The other three women’s matches were moved to Saturday.

Storms earlier in the week forced some men to play twice in one day.

Murray’s third-round victory over Marius Copil ended just past 3 a.m. on Friday, after rain delayed the start of Thursday’s action for 2 1/2 hours. Afterward, Murray told a small group of reporters that he “potentially” could withdrew from the tournament.

He also announced Friday that he was going to skip next week’s Toronto Masters.

Murray is working his way back into form after having surgery on his right hip and being sidelined for 11 months.

“I’m exhausted after playing so much over the last four days, having not competed on the hard courts for 18 months,” said Murray, whose three matches each lasted more than 2 1/2 hours. “I also need to be careful and to listen to my body as I come back from a long-term injury.”