Crowds were told to leave the stadium as the match carried on past midnight and Melbourne’s five-day lockdown came into force.
While the 33-year-old Djokovic had enough in the tank to defeat world No. 31 Fritz, the world No. 1 admitted after the match that he may not be able to recover from the abdominal injury he sustained before facing Milos Raonic in the next round on Sunday.
“Right now, I know it’s a tear … I don’t know if I’ll manage to recover from that in less than two days,” Djokovic said of the injury that hampered his movement in the second half of the match.
“I don’t know if I’m going to step out onto the court or not. I’m very proud of this achievement tonight, let’s see what happens tomorrow.”
Djokovic marched into a two-set lead against the big-serving Fritz before the momentum of the match shifted.
The Serbian had to leave the court for treatment as 23-year-old Fritz took the next two sets to level the contest.
But Djokovic summoned enough strength to take the final set and let out a roar of relief when he converted a match point.
“This is definitely one of the most special wins in my life, it doesn’t matter what round it is and who it is against, under these kind of circumstances to pull this through is definitely something I’ll remember forever,” he added in his post-game interview.
The second five-set encounter of the day after Dominic Thiem’s comeback victory against Nick Kyrgios, Djokovic and Fritz completed the game in an empty Rod Laver Arena as spectators were forced to leave ahead of the Melbourne quarantine.
The state of Victoria is locking down from Saturday in a bid to curb the spread of a more contagious virus variant, although the Australian Open has been allowed to continue in the absence of fans.