Did Fearnley, who was outside the world top 500 before winning a Challenger tournament last month, play out of his skin?
Or is Djokovic not really ready to compete at the elite level a month after surgery on a torn meniscus in his right knee.
The answer appears to be a bit of both, which offers a degree of hope for Djokovic's next opponent, Australia's Alexei Popyrin, and to Alex de Minaur who is seeded to face the 24-times grand-slam champion in the quarter-final should both progress.
De Minaur's chances of making that date improved after seventh-seed Hubert Hurkacz - his probable fourth-round opponent - retired with a knee injury.
But will Djokovic be there? He beat Fearnley 6-3 6-4 5-7 7-5, but the seven-times Wimbledon champion admitted the match could easily have gone the distance.
Rank outsider Brit Jacob Fearnley delighted Centre Court when he took a set off Novak Djokovic. (EPA PHOTO)
"Huge congrats to Jacob for an amazing match," he said.
"This match potentially deserved to get into a fifth the way we both played, the way he played particularly in the fourth, but I'm very glad it didn't."
Djokovic is 37 now, and the strapping on his knee - which is still grey, not Wimbledon white - is a reminder of his mortality.
"I do feel that has an impact on my movement a little bit in terms of the speed," Djokovic said.
"It's not yet there where I want it to be. I'm kind of late on the balls that I'm normally not late on.
"That's the part which I guess comes with matches. The earlier rounds are where I'm still a little bit rusty on the movement."
Hurkacz quit when he was 9-8 down in a fourth set tiebreak against 20-year-old Frenchman Arthur Fils, who was leading 7-6 (7-2) 6-4 2-6 6-6.
"It's tough to win a match like this against a friend," Fils said.
"We were playing super-good in the fourth. We had some great points. He was jumping everywhere. I'm really sorry for him."
Having made a slow start, Hurkacz was on course to level the match at two sets apiece when he dived for a volley at the net in the fourth set tiebreak to go 8-7 up, but landed badly and clutched his right knee.
The Pole limped on after a lengthy medical timeout, but was forced to throw in the towel two points later.
Fils became the youngest Frenchman to reach the Wimbledon third round since 2005, when Richard Gasquet and Gael Monfils did so as teenagers.
Monfils, now 37, is still going. He sealed a hard-fought 7-6 (7-5) 6-4 7-6 (7-3) win over 39-year-old Stan Wawrinka.
Fourth seed Alexander Zverev had no trouble seeing off Marcos Giron in three sets, but Finland's Emil Ruusuvuori stunned 11th seed Stefanos Tsitsipas 7-6 (8-6) 7-6 (12-10) 3-6 6-3.
In seven visits to the All England Club Tsitsipas has yet to make a quarter-final.
Grigor Dimitrov, the 10th seed, Ben Shelton (14th) and Holger Rune (15th) all came back from a set down to defeat, respectively, Shang Juncheng, Lloyd Harris and Thiago Seyboth Wild.
Cameron Norrie beat the man who has replaced him as British No.1, Jack Draper, 7-6 (7-3) 6-4 7-6 (8-6) while American 13th seed Taylor Fritz needed four sets to see off the stubborn Frenchman Arthur Rinderknech.
There was edge between the pair after a tense meeting at Roland Garros, and at the net Fritz said, "Have a nice flight home".
According to Fritz, Rinderknech responded by pointing out he's still around in doubles.
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