CINCINNATI, United States (AFP) — US teen wildcard Frances Tiafoe shocked seventh-ranked Alexander Zverev 4-6, 6-3, 6-4 yesterday, advancing to the third round at the WTA and ATP Cincinnati Masters.

Riding a 10-match win streak after titles in Montreal and Washington, Zverev was a favorite to capture his seventh title of the year in the last major US Open hard court tune-up.

But 19-year-old Tiafoe, a second-round loser to the 20-year-old German at Wimbledon and the Australian Open in their only prior meetings, pulled off the greatest triumph of his young career.

“I can’t believe it,” Tiafoe said. “To win a match like that was great for me.”

Zverev said the toll of his extraordinary run caught up with him this week.

“I’m completely dead right now,” Zverev said.

Zverev broke Tiafoe with a forehand winner to claim the first set, but the American, cheered on by a host-nation crowd, replied by breaking Zverev in the first, third and ninth games of the second set, forcing a third with a backhand winner.

Rafael Nadal, who returns to the world number one spot Monday for the first time since 2014, was set to later face France’s Richard Gasquet in a second-round match. The 31-year-old Spaniard has a 14-0 career ATP record against Gasquet.