Djokovic, 38, beat Tien, 6-1, 7-6, 6-2 to improve to 19-0 in US Open first-round matches, tying Roger Federer for first all-time. But he labored with low energy, a nasty blister on his right big toe and Tien’s level, especially in the second set.

Novak Djokovic may still be going strong at 38, holding his own against the new generation led by Carlos Alcaraz and Jannik Sinner, but even he knows he can’t play forever. As the last active member of the legendary “Big Three,” every tournament he enters feels like a reminder that tennis is inching toward the end of an era.

Novak Djokovic looked tired. He looked hurt. And at times Sunday night, he just looked old. Djokovic overcame all that and improved to 19-0 in the first round of the US Open, battling through some leg troubles to beat Learner Tien 6-1,