Rising star Carlos Alcaraz saved a match point and fought back from an early deficit in the fifth set to beat Albert Ramos-Vinolas at Roland Garros.
The No.6 seed won six of the final seven games, and the final half-dozen points, to win 6-1 6-7 (9-7) 5-7 7-6 (7-2) 6-4.
His second-round victory on Wednesday lasted more than four and a half hours but he came perilously close to a surprise defeat.
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Alcaraz is just 19 but arrived in Paris with a lot of expectations – his own and others’ – based on a breakthrough season that has brought him a tour-leading four titles.
He is the youngest player to break into the top 10 of the ATP rankings since Rafael Nadal in 2005.
En route to the Madrid Open title on red clay earlier this month, Alcaraz became the first man to beat both Nadal and Novak Djokovic in the same tournament on that surface.
But he was quite close to making a quicker-than-anyone-expected exit against fellow Spaniard Ramos-Vinolas, a 34-year-old who is ranked No.44.
Alcaraz was a point from losing while Ramos-Vinolas served for the victory at 5-4 in the fourth set.
But Ramos-Vinolas missed a forehand and, 80 minutes later and after trailing 3-0 in the fifth, Alcaraz earned his first match point and converted it with an ace.
Alcaraz is now unbeaten for 12 straight matches after bagging back-to-back titles in Barcelona and Madrid going into Roland Garros and will next face American Sebastian Korda.
“I am still young but I am an experienced player now,” Alcaraz told a news conference.
“I feel comfortable playing in big stadiums, big matches, Grand Slams. I am ready to play these kind of matches in these situations.
“I want to play big battles and top battles against the best players in the world,” he said. “Being number one is my dream since I stated playing tennis.”
Alcaraz had looked unflustered by the blustery conditions in the first set but his error count grew and he survived a match point at 5-4 in the fourth set before forcing a decider.
“I knew that I would have my chance in the end of fourth set. I believed in myself the whole time. In the fourth and fifth set I was smiling with my team,” he said.