Novak Djokovic, a 24-time Grand Slam champion, fought back from a set down to defeat American qualifier Zachary Svajda at the US Open, winning 6-7 (5-7) 6-3 6-3 6-1.
The Serb, who admitted he isn’t playing his best tennis, said he is “trying to solve the riddle” of his form as he pursues a record 25th major title.
He will face Britain’s Cameron Norrie in the third round.
In other matches, second seed Carlos Alcaraz advanced easily, and a number of top Americans, including Taylor Fritz, Ben Shelton, and Frances Tiafoe, also secured wins.
The biggest upset of the day was 12th seed Casper Ruud’s loss to Belgium’s Raphael Collignon.
The defeat caps a disappointing Grand Slam year for Ruud, who has had early exits in all three majors he has played.
