Djokovic describes the Australian Open as his “second home”, where he has dominated over the years, and this was another impressive display as he beat the latest younger challengers on Rod Laver Arena.
The victory means that the last defeat for the Serbs in Melbourne remains the fourth round loss to South Korea's Chung Hyun in 2018.
With the match kicking off at around 17:00 local time in 31°C temperatures, Djokovic created eight break points in the first set but became increasingly confused as he was unable to convert any of them.
The 24-time major champion – who appeared frantic, regularly using icy towels and shouting in the direction of his team – was almost punished when the 26-year-old created two set points at 6-5 with a stunning forehand down the line.
However, Djokovic found his composure to save them, paving the way for him to pounce in the tie-break.
With the help of Fritz missing a volley to make the score 1-0, Djokovic quickly asserted his control and took the first set after 84 minutes.
The American player, who lost all eight of his previous meetings with Djokovic, responded valiantly.
A break in the first game of the second set, before fighting off seven more break points, enabled Fritz to level the score.
But Fritz began to suffer from a foot problem and Djokovic looked strong as the atmosphere improved and he broke serve twice to win the third set.
With Djokovic in complete control, he was under little pressure on his serve, and when he broke to level the score at 4-2 in the fourth set, the match seemed headed towards the end.
Fritz bounced back, hitting a volley to take Djokovic's serve, but the Serb broke again before serving powerfully.
Djokovic said: “The conversion of break points was really bad, but I think at the end of the day I was able to break him when it mattered in the third and fourth sets.”
“I upped my game probably midway through the third set to the end.”
