NEW YORK — Stan Wawrinka is the first to acknowledge he hasn't always been the most consistent player — or the strongest mentally. That's why, when he shows his mettle during a match, he likes to point his right index finger to his temple.

That signature gesture got a lot of use in the U.S. Open final Sunday, when Wawrinka surprisingly managed to wear down Novak Djokovic and beat the defending champion 6-7 (1), 6-4, 7-5, 6-3 for his first U.S. Open title and third Grand Slam trophy overall.

“He was the better player. He was tougher mentally,” said Djokovic, offering two of the highest compliments a tennis player can receive from the talented and sturdy Serb ranked No. 1. “He knew what to do. And I was just unlucky in some moments. And that's it.”

The 31-year-old Wawrinka is the oldest U.S. Open men's champion since Ken Rosewall was 35 in 1970 and entered Sunday having spent almost exactly twice as much time on court as Djokovic during the course of the tournament: about 18 hours versus about 9 hours.

“I played quite a lot of tennis these two weeks. I am completely empty,” No.?3 Wawrinka said.

By breaking in the final game of the second and third sets, and by saving 14 of 17 break points he faced, Wawrinka already had gained the upper hand by the time Djokovic clutched at his left leg and grimaced after missing a forehand while getting broken early in the fourth.

Djokovic was granted the unusual chance to have a medical timeout at a time other than a changeover. He removed both shoes and socks so a trainer could help with toe blisters. Wawrinka complained about the 6-minute break, and Djokovic looked over and apologized. Later, Djokovic started limping and received more treatment.

“Wawrinka has won only five of his 24 career meetings against Djokovic, but has now beaten the 12-time major champion on the way to each of his own Grand Slam titles, including in the 2014 Australian Open quarterfinals and 2015 French Open final.