The 19-year-old from Irvine, California nearly lost a two-set lead from match point up but held off a late surge from a former world No. 1 to win the biggest match of his career.

There are six American men and five American women in the third round. Tommy Paul, Coco Gauff and Jessica Pegula all play Thursday. No. 17 Frances Tiafoe, a two-time U.S. Open semifinalist, was upset ...