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.
This marks the third time in his career he's achieved that impressive double, winning Wimbledon and US Open titles back-to-back in 2011, 2015 and now 2018.
But he could not take either and, once Djokovic broke to lead 3-2, it merely seemed a question of how much resistance his opponent could muster. But then he was broken in his next game.
Between them, Federer, Nadal and Djokovic have won 47 of the last 55 slam titles, but Del Potro has no regrets, saying: "It is a big challenge to take these kind of tournaments from them".
They are also atop another important ranking: most career Grand Slam titles by a man. Federer holds the record of 20, followed by Nadal with 17, and Djokovic, who equaled Pete Sampras at 14.
For quite some time after that Djokovic looked towards Del Potro's singing friend with utmost anger, unable to get them out of his head and that showed on the court.
After the controversy surrounding Serena Williams' defeat by Naomi Osaka in Saturday's women's final, a high-quality match between two of the top male players ensured tennis was once again the talking point. "To be honest, I was crying till now", Del Potro said as he began his post-match press conference.
This year he defeated Federer in the Indian Wells Masters final while in 2016 he was a key figure as Argentina won a first Davis Cup. "To see her being so dedicated and so committed to this sport, it's inspiring to me and to many tennis players, both men and women, around the world".
The Wimbledon champion, who ended a two-year grand slam drought by winning at the All England Club, has now won 13 sets in a row in NY. He has come to the conclusion that his time away during rehabilitation re-energized an already rousing career.
Sloane Stephens, who won last year's U.S. Open and lost in the quarterfinals last week, dropped from No. 3 to No. 9.
"Today I really am". But I was playing at the limit all the time, looking for winners with my forehands, backhands, and I couldn't make them because Novak was there every time. The first actual thing I saw related to tennis on the TV was his first or second Wimbledon championship.
The 2.4 overnight rating is up 32% from past year (1.9 for Sloane Stephens and Madison Keys of the U.S.) and 79% higher than 2016 (1.4 for Angelique Kerber vs. Karolina Pliskova).
"I was hoping [Pete Sampras] was going to be here tonight", Djokovic said during the awards ceremony.
There may have been no game more important to Djokovic's win or simply entertaining than the eighth game of the second set.
Djokovic captured the first of his 12 majors in Melbourne in 2008, but it was three years before he added his second.
Now he is back up to three and within striking distance of Nadal in the race to finish the season ranked world number one.