Alexander Zverev serves during his match against Lloyd Harris on Wednesday in Mason, Ohio. Photo: VCG

Olympic champion Alexander Zverev struck gold at the ATP Cincinnati Masters on Wednesday with his first victory at the US Open tuneup event in seven attempts.

The German has been deep in a rut from his first appearance in 2015 at the Midwest US venue, exiting in the first round every time.

But that all changed as Zverev celebrated success with a 7-6 (7/3), 6-2 win over South African Lloyd Harris to break his duck.

"I'm happy where I'm at and I'm happy to get my first win in seven years here," he said. "It's obviously a great start to the week."

The breakthrough victory was the seventh in a row for the 24-year-old.

"When I came on court and they said Olympic gold medalist, it did give me goose bumps," Zverev said.

"It made me a little nervous at the beginning of the match, I have to say, because it is a special feeling."

Zverev now goes up against Argentine Guido Pella, a winner over Italy's Fabio Fognini 6-1, 7-5.  

Top seed Daniil Medvedev, last week's Toronto champion, also advanced in a no-drama 6-2, 6-2 defeat of American Mackenzie McDonald that took just an hour for the 2019 Cincinnati champion.

No.2 seed Stefanos Tsitsipas fought off Sebastian Korda for a 7-6 (7/5), 6-3 victory that took the Toronto semifinalist into the third round.

The Greek won on his second match point as Korda drove a forehand long after 97 minutes.

Tsitsipas next plays Italy's Lorenzo Sonego who beat American Tommy Paul 7-6 (11/9), 6-2.

Norway's eighth-seeded Casper Ruud out-aced American Reilly Opelka 21 to 17 on his way to a 6-7 (5/7), 6-0, 7-6 (7/4) victory.

Andy Murray's wild card run ended with a 7-6 (7/4), 6-3 loss to Poland's Hubert Hurkacz.

The Scotsman, who has been struggling to reestablish himself on tour after his latest injury - a groin problem - lost the second-round contest in one and three-quarter hours to the player who knocked Roger Federer out of Wimbledon.

Murray fired a respectable 11 aces to the 17 of his ninth-­seeded opponent in the first-time meeting while saving four break points.

"This week was fairly positive. I played much better than at Wimbledon and the grass season," he said. "This week my body felt good, even if hard courts are not easy on the body.

"Physically I was tired after some of the long rallies, but I felt fine."

The 34-year-old Briton said the only factors that would make him reconsider his comeback were "if my body doesn't feel good" or "my tennis starts going backwards."

The two-time Cincinnati winner, ranked 105th, owns 14 career Masters 1000 titles, the most of any man in a field missing the "Big 3" trio of Federer, Rafael Nadal and Novak Djokovic - all 20-time Grand Slam champions.

Olympic silver medalist ­Karen Khachanov joined Murrray in defeat as the Russian exited 6-7 (5/7), 6-3, 6-4 to Canada's 12th-seeded Felix Auger-­Aliassime, who will face Wimbledon finalist Matteo Berrettini for a quarterfinal place.

Frenchman Gael Monfils earned the 500th match win of his career as he beat Australian Alex de Minaur 6-3, 7-5. ­Victory put the 34-year-old into the third round against sixth seed Andrey Rublev, aged just 6 when the Frenchman won his first ATP match in 2004.

"It was at Metz against Xavier Malisse and he retired," Monfils said. "I remember all of my wins. I've been on the Tour a long time."

American John Isner beat Italian 11th seed Jannik Sinner 5-7, 7-6 (7/4), 6-4.

Former champion Grigor Dimitrov reached the third round over Kazakh Alexander Bublik 6-3, 7-5.