NEW YORK — The rankings do not yet reflect it, but there can be no doubt which man is playing the finest tennis in the world.

On his last visit to U.S. hard courts, in March, Novak Djokovic looked like a man in a dinghy without a motor or a sail, losing his opening-round matches in Indian Wells, California, and Miami.

But that confounding trip, part of a malaise that lasted nearly two years, is now part of the past.

After returning to the fore by winning Wimbledon in July, he returned to dominance by winning the U.S. Open for the third time Sunday night.

His 6-3, 7-6 (4), 6-3 victory over Juan Martín del Potro under a closed roof at Arthur Ashe Stadium was a brilliant display of Djokovic’s suffocating skill set.

It was all there: the precision serving, the fast-twitch returns, the baseline consistency under greatest pressure, and, above all, the full-stretch defense that can buckle the knees and spirit of even a player as resilient as del Potro.

Djokovic has routinely gone deep at the Open, but he was often stopped just short of the biggest prize. But he is 3-5 in Open finals and is tied with former American star Pete Sampras for third on the career list with 14 Grand Slam singles titles.

The best duel of the night was Djokovic’s world-class defense against del Potro’s world-class forehand, which remains one of the game’s ultimate crowd pleasers.

“When I had the surgery on my elbow earlier this year, I could truly understand what Juan Martín was going through with his surgeries,” Djokovic, 31, said in the post-match awards ceremony. “But you learn from adversity. You learn when you’re down and when you have doubtful moments, when things are not working out as you want them to. I try to take the best out of myself in those moments and thrive on the support and love I get from close ones to get myself in this position.”