(Reuters) – Rafa Nadal extended his spotless record against Richard Gasquet, while unseeded American teenager Frances Tiafoe upset Alexander Zverev to reach the third round of the Cincinnati Open on Wednesday.

It must have felt like deja vu for the Frenchman, who fell 6-3 6-4 to drop to 0-15 against Nadal. Gasquet last won a set against the Spaniard in 2008.

Nadal, who repelled the only break point he faced in the match, served out the match at love in the 10th game, firing in three aces, including the finishing point.

“I work every day to play better. It’s obvious that was an important start for me, a good one,” said French Open champion Nadal, who will claim the world number one spot on Monday.

“Now I have another opportunity tomorrow to go on court and play.”

The 15-times grand slam winner will next face fellow Spaniard Albert Ramos-Vinolas, who eliminated Nadal’s Wimbledon conqueror, 16th seed Gilles Muller of Luxembourg, 5-7 6-4 6-4.

World number seven Zverev, who stunned Roger Federer in the Montreal final last week after claiming the title in Washington D.C., was on a 10-match winning streak but faded in the final set against energetic baseliner Tiafoe, who won 4-6 6-3 6-4.

It was 19-year-old Tiafoe’s first win over a top-10 player and he bounded around the court in joy, thumping his chest to a standing ovation after Zverev floated a backhand long on match point with his third unforced error of the last game.

“I saw he was a bit tired, but he was still competing. It was tough. I was happy to get through it,” 87th-ranked Tiafoe told Tennis Channel. “My game plan was to keep the rallies long and keep him out there and that’s what I did.”

Tiafoe will meet John Isner next and said he knows he will be tested by his compatriot’s booming serve.

“I just got to weather the storm,” Tiafoe said. “He’s going to drop some big-boy heat on me and I’m going to have to be ready for it.”

Zverev, 20, was not dismayed too much by the defeat and said he was looking forward to the U.S. Open later this month.

“I think Roger (Federer) and Rafa are the strongest ones and a few guys coming after that. I think I am involved in that group. I am in that small group of players,” the German said.

“So I feel very confident the way I was playing in the last two weeks. And I think going into the U.S. Open, I feel the best I have ever felt maybe going into a slam.”

Earlier, Bulgarian seventh seed Grigor Dimitrov beat Feliciano Lopez 7-6(5) 6-4 to set up a last-16 clash with Juan Martin del Potro.

Del Potro advanced with a 6-4 6-4 win over American qualifier Mitchell Krueger, winning each set on a late break.

Dimitrov has not beaten Del Potro in five career meetings, with the most recent defeat coming at Rome in May.

Australian Nick Kyrgios beat Ukraine’s Alexandr Dolgopolov 6-3 7-6(6) to reach the third round, where he will face unseeded Croatian Ivo Karlovic.