Djokovic glared at the crowd and tossed his hands up in disbelief after losing one 16-shot rally, then he steadied himself and fended off three game points that would have given del Potro a two-game lead in the set.
With all the singing and noise levels inside the stadium, it felt to Djokovic like he was at a football match but he thanked the fans of both sides for creating such an fantastic atmosphere.
Del Potro spoke this week about the low point, in 2015, when he considered quitting the sport.
The effort took its toll on a suddenly weary-looking Del Potro as a 95-minute set was claimed by Djokovic in the tiebreak.
"We are proud to be close to these legends", Del Potro said.
No controversy here: Novak Djokovic is the U.S. Open men's singles champion.
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Djokovic, who won Wimbledon in July, has now won 14th grand slam titles - putting him level with Pete Sampras and behind only Roger Federer (20) and Rafael Nadal (17) on the all-time list. It's not just like, 'Okay, see you later, I've got to go'.
Del Potro was looking at having to become the first man since Pancho Gonzales in 1949 to win the United States title from two sets down.
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.
Djokovic was better than del Potro on their many lengthy exchanges, using his trademark body-twisting, limb-splaying court coverage to get to almost every ball, sneakers squeaking around the blue court in Arthur Ashe Stadium, where the roof was closed because of rain.
With the quality of tennis only on the rise, the noise level inside the Arthur Ashe Stadium was deafening.
Former world no. 1 missed the US Open last year due to a bothersome elbow that required surgery but post-surgery, Djokovic has returned to the fray and looks confident to lift the title this year.
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With the Arthur Ashe Stadium roof closed as heavy rain swept NY, conditions were slow and sluggish.
"To support of my loved ones, my kids, my wife, my team of people that has been there with me through hard times as well".
"Difficult times but you learn from adversity".
"When I had the surgery on my elbow I could truly understand what Juan Martin was going through", Djokovic said.
Amidst the searing heat and disturbing humidity of NY for the past two weeks, Djokovic battled through and rose above it all to shine under the Arthur Ashe Stadium lights for the third time.
"I'm so happy to be playing the final against this magnificent idol".
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Djokovic went on to congratulate Del Potro for his achievements despite all the injury trouble and made a massively sporting gesture by saying he knew Del Potro will stand as champion at this podium one day.