CINCINNATI, Ohio (AFP) - US teen wildcard Frances Tiafoe shocked seventh-ranked Alexander Zverev 4-6, 6-3, 6-4 on Wednesday (Aug 16), 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 hardcourt tuneup.
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 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.
After exchanging breaks to open the final set, Zverev rescued a break point to level 4-4, Tiafoe and held and forced two break and match points. When Zverev sent a forehand long, Tiafoe screamed for joy.
Tiafoe will face US 14th seed John Isner in the third round.
Zverev could have matched Andre Agassi in 1995 with the only ATP Washington, Canada and Cincinnati title hat trick in a year.
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.
Bulgaria's 11th-ranked Grigor Dimitrov, the only seeded player in his quarter of the draw, downed Spain's Feliciano Lopez 7-6 (7/5), 6-4, to reach a third-round match against Argentina's Juan Martin del Potro.
Australian 48th-ranked qualifier Ashleigh Barty upset ninth-ranked American Venus Williams 6-3, 2-6, 6-2 for her first win over a top-10 foe.
"It's amazing to beat a great player like Venus," Barty said. "I'm really happy."
Barty, 21, broke Williams, 37, in the sixth game and held twice more to take the first set in 36 minutes.
In the third set, Barty broke the seven-time Grand Slam champion twice for the triumph, leaving the Wimbledon and Australian Open runner-up more rest time for the US Open than she really wanted.
"I'm going to take a break and have a rest and just go be," Williams said. "I'm just planning on being super rested." Top-ranked defending champion Karolina Pliskova was set to open later against Russian lucky loser Natalia Vikhlyantseva with the Czech's world number one status at risk this week.
She could be overtaken by Romania's Simona Halep, Ukraine's Elina Svitolina or Dane Caroline Wozniacki, who advanced past Russia's Elena Vesnina 6-2, 6-4.
Germany's Angelique Kerber, who lost the top spot following Wimbledon, missed her chance to reclaim number one by losing to Russia's Ekaterina Makarova 6-4, 1-6, 7-6 (13/11).
A thrilling tie-breaker in the battle of left-handers saw Makarova save a match point and Kerber deny her on seven match points before the Russian's forehand drop volley winner ended the marathon after two hours 38 minutes, lifting her to 5-0 this season against top-5 foes.