A decade or so ago, back when Tommy Paul, Taylor Fritz and Frances Tiafoe were rowdy teenagers raising hell at the United States Tennis Association dormitories in Florida, they dreamed that days like Sunday at the U.S. Open would eventually come.

Coco Gauff and Ben Shelton were barely 10 years old back then, still figuring out how large a role tennis was going to play in their childhoods, though it was a safe bet it would be pretty large.