And then came Sunday's pivotal game, a 20-minute, 22-point epic. Three times, del Potro was a point from breaking and earning the right to serve to make it a set apiece. Three times, Djokovic steeled himself. Eventually, he seized that game — and del Potro's best chance to make a match of it.

A year after missing the U.S. Open because of an injured right elbow that would require surgery, Djokovic showed that he is unquestionably back at his best and back at the top of tennis. His returns and defense-to-offense skills as impeccable as ever, Djokovic collected his 14th Grand Slam title and second in a row by getting through every crucial moment for a 6-3, 7-6 (4), 6-3 victory over 2009 champion del Potro at Flushing Meadows.

"There was always part of me that imagined and believed and hoped that I can get back (to) the desired level of tennis very soon," said Djokovic, whose operation was in February. "But at the same time, life showed me that it takes time for good things, it takes time to really build them, for things to fall into place, so you can center yourself, balance yourself and thrive. The last two months have been terrific."

This was Djokovic's third championship in New York, along with those in 2011 and 2015. Add in the trophies he has earned at six Australian Opens, one French Open and four Wimbledons, most recently in July, and the 31-year-old Serb pulled even with Pete Sampras for the third-most majors among men, trailing only Roger Federer's 20 and Rafael Nadal's 17.

""He's my idol. Pete, I love you," Djokovic said.

Federer lost in the fourth round in New York, while Nadal retired from his semifinal against del Potro because of a bad right knee. That put the 29-year-old Argentine back in a Grand Slam final for the first time since his breakthrough nine years ago, a comeback for a guy who had four wrist operations in the interim.

"I believe he'll be here again with the champion's trophy. I really do," said Djokovic, who gave his pal a hug at the net, and then went over to console del Potro as he wiped away tears at his sideline seat.

Del Potro spoke this week about the low point, in 2015, when he considered quitting the sport. But supported by a dozen or so friends from back home, whose "Ole!" choruses rang around the arena, he climbed up the rankings to a career-high No. 3 by thundering his 100 mph (160 kph) forehands and 135 mph (215 kph) serves.

Those produce free points against so many foes. Not against Djokovic, who always seemed to have all the answers — and who said he convinced himself that all of those "Oles" were actually people calling out his own nickname, "Nole."

Djokovic was better than del Potro on their many lengthy exchanges, using his trademark body-twisting, limb-splaying court coverage to get to nearly every ball, sneakers squeaking around the blue court in Arthur Ashe Stadium, where the roof was closed because of rain.

"I was playing almost at the limit, all the time, looking for winners with my forehands, backhands, and I couldn't make it," del Potro said, "because Novak (was) there every time."

Never was that more apparent than the game that stood out on this evening, with Djokovic serving while down 4-3 in the second set. They went back and forth, through eight deuces and all those break opportunities for del Potro, until he slapped one forehand into the net, and another sailed wide.

Those were high-risk shots, but, as del Potro put it: "It's the only way to beat these kind of players."

Djokovic's coach, Marian Vajda, called that moment the match's "turning point, obviously."

When it ended, with Djokovic holding to 4-all, spectators began leaving their seats, perhaps thinking it was time for a changeover, even though it wasn't. That prompted to chair umpire Alison Hughes to chastise them.

It was a brief request, though, unlike her many other pleas for quiet, mainly as fans were shouting and chanting and clapping in support of del Potro. It all bothered Djokovic, who started yelling and gesturing toward the seats. At one moment, he pressed his right index finger to his lips, as if to say, "Shhhhhhh!" Later, after winning a point, Djokovic put that finger to his ear, as if to say, "Who are you cheering for now?!"

The tiebreaker was resolved thanks to more del Potro miscues on his forehand side, as he looked more and more fatigued. He made one last stand by breaking and holding for 3-all. But that was that.

When it ended, thanks to a three-game closing run by Djokovic, he flung his racket away and landed on his back, arms and legs spread wide.

He had hit his peak, Vajda said, at "just at the right time."

Djokovic had never gone through an extended absence until 2017, when he sat out the second half of the season because of elbow pain that had plagued him for more than a year. He tried to return at the start of this season, but couldn't, and opted for surgery.

It took him some time to find the right form, as evidenced by his quarterfinal loss at the French Open to a guy who was ranked 72nd and had never won a Grand Slam match until that tournament.

"I was very, very disappointed with my performance that day," Djokovic recalled Sunday, explaining that he went hiking in the mountains in France to clear his head after that setback.

Djokovic then got right back to work, and announced that he was, once more, himself by winning Wimbledon.

Now he's backed that up at the U.S. Open, the fourth time in his career he won multiple majors in a season.

"Difficult times, but you learn through adversity," Djokovic said. "I try to take the best out of myself in those moments."