In just the second United States Open singles match of her life, 15-year-old Coco Gauff did an excellent impression of a veteran on Thursday night: keeping her cool, measuring her risks and making the shots that mattered most.

Her 6-2, 4-6, 6-4 victory over Tímea Babos, a 26-year-old qualifier from Hungary, was a thing of grit and beauty. It made Gauff, a fleet and resourceful American, the youngest player to reach the third round in singles at the U.S. Open since Anna Kournikova in 1996.

Things won’t get easier or less floodlit from here. Gauff’s third-round opponent will be none other than Naomi Osaka, the world’s No. 1 player and the defending U.S. Open champion.

Informed of that matchup during a post-victory interview in Louis Armstrong Stadium, Gauff nodded calmly at first. Then the near-capacity crowd at the tournament’s second biggest show court produced a collective “ooooh,” and she reacted to that reaction by smiling and shrugging her shoulders.