He demonstrated it again Sunday, upsetting the world No. 1, 6-7 (1-7) 6-4 7-5 6-3, in a bruising four-hour US Open final to win a third grand slam title. To the side of the court on Arthur Ashe stadium in New York, "9/11/01" was inscribed 15 years after the September 11, 2001 attacks in the city.
Djokovic sizzled at the start, racing to a 4-1 lead. But in allowing Wawrinka to find his way into the first set, the match veered in a different, and for Djokovic, displeasing direction. Djokovic was broken to end the second and third sets, before suffering physically in the fourth. Normally ruthless in converting break points, he slumped to 3-for-17.
The 31-year-old Wawrinka possesses thunderous strokes able to penetrate the perhaps unparalleled defense of Djokovic, with his versatile one-handed backhand attracting the majority of the plaudits. But don't forget the forehand, which is among the most punishing around.
Wawrinka, who struck a stunning 46 winners, became the oldest men's champion at the US Open since Ken Rosewall in 1970.
"This honestly is amazing," Wawrinka said during the trophy presentation. "I came here without putting a goal to win (the tournament) but every time I stepped on the court I was trying to win every match.
"I think I played quite a lot of tennis these last two weeks. I'm completely empty. I had to bring everything I had today against Novak."
Whereas Djokovic has won four grand slam matches in a row against Wawrinka's fellow Swiss, Federer, five straight against Murray and the only one he contested against Nadal since 2015, he is merely 3-3 in his last six against Wawrinka.
Who was the last player to down Djokovic in a grand slam final? Wawrinka, at the 2015 French Open when he also conceded the first set. Now he took a bite out of Djokovic in the Big Apple.
This after saving a match point against Dan Evans in the third round. How Djokovic must have wished Evans completed the job.
Djokovic called Wawrinka the "more courageous player."
"In the decisive moment, he was the better player, he was tougher mentally, he knew what to do and I was just unlucky in some moments," said Djokovic. "That's it. A few points decide a winner at this level."
Wawrinka refuses to be featured in any "Big Five;" he feels the other four are much more consistent. Indeed he sometimes suffers baffling losses, yet the deeper he progresses at events, the more dangerous he becomes: He has won his last 11 finals.
Djokovic benefited from unprecedented luck at this US Open -- three of his opponents either retired or withdrew before the semifinals -- but perhaps it still wasn't enough to mend an array of injuries. Or, did he not play enough tennis?
He arrived at the US Open with a well-publicized wrist injury, then had his arm and both shoulders worked on by the trainer in matches during the fortnight. In the fourth set against Wawrinka, he took two medical timeouts for what appeared to be toe issues.
The first one irked Wawrinka, since it happened not during a changeover -- which is the norm -- but at 3-1. Djokovic apologized while receiving treatment.
"It was a fantastic couple of weeks for me," said Djokovic. "I didn't know if I was going to come a few weeks before (the tournament). I was thinking, 'Should I come or not' because I struggled physically but if someone told me I was going to play in the final I would definitely take it."
Not until the Australian Open in January will Djokovic, who has spoken of his desire to match Federer's leading men's haul of 17 majors, get his next opportunity to collect a 13th grand slam title.
While Djokovic concludes the grand slam season as the lone men's player to win two major titles, he came up empty at his last two.
He was unable to build on the momentum of the first-set tiebreak against Wawrinka, which featured a breathtaking Djokovic backhand down the line immediately after his rival had just won a highlight-reel point of his own.
If he was deflated, Wawrinka got help from Djokovic in the fourth game of the second. Djokovic was broken from 40-15, donating a pair of double faults in the game.
Wawrinka padded his advantage to 4-1, was pegged back to 4-4 but leveled the affair when Djokovic missed a forehand.
Djokovic's frustration grew. He smashed his racket -- then fell behind 0-3, 0-30 in the third. When he hung on and found himself at 4-4, one began to wonder if all the time Wawrinka spent on court -- almost double that of Djokovic ahead of the final -- would catch up with the world No. 3.
Wawrinka almost dropped serve from 40-0 in the ninth game -- taken to deuce -- and had to escape from 15-30 at 5-5. Djokovic blew a game point at 5-6.
Djokovic had never come from 2-1 down in sets to win a grand slam final and his task grew harder given his toe problems. Yet after the medical timeout at 3-1, he held break points. But this wasn't Djokovic's night in New York.
Wawrinka offered heartfelt praise to Djokovic in the aftermath, saying: "You are a great champion, great person, because of you I am where I am today."
Wawrinka has become a great champion, too -- but someone Djokovic won't want to see on the other side of the net in a grand slam anytime soon.