Super Spaniard Alcaraz advanced on Sunday afternoon when his fourth round opponent, 15th-seed Brit Jack Draper, was forced to withdraw with a hip injury while trailing 7-5 6-1.
Ten-time champion Djokovic then overcame 23-year-old Czech Jiri Lehecka on Rod Laver Arena in the evening, winning 6-3 6-4 7-6 (7-4) to keep alive his quest for a record 25th grand slam singles title.
With his 10-year-old son Stefan, a rare visitor to the Open, watching in the stands, Djokovic sealed his 15th quarter-final appearance - equalling Roger Federer's all-time record at Melbourne Park.
He also stretched his all-time record for grand slam quarter-final appearances to 61.
Novak Djokovic explained his refusal to be interviewed by Channel Nine was a protest. (James Ross/AAP PHOTOS)
Djokovic refused to partake in the usual on-court interview, only taking a moment to thank the crowd.
He explained in a later press conference that it was in protest to treatment by host broadcaster Channel Nine, and one of the hosts Tony Jones.
During a live broadcast on Friday night, the newsreader mocked Serbian fans as well as Djokovic.
"A couple of days ago, a famous sports journalist who works for official broadcaster Channel 9 here in Australia made a mockery of Serbian fans and also made insulting and offensive comments towards me," Djokovic said.
"Since then, he chose not to issue any public apology, neither did Channel 9, so since they are official broadcasters, I chose not to give interviews for Channel 9.Â
"I leave it to Channel Nine to handle this the way they think they see fit."
Djokovic said he would continue to boycott the station until he received an apology.
Lehecka posed a genuine threat to the veteran after an eight-match unbeaten start to the year, which included the Brisbane International title.
He had only dropped one set in three Open matches, while his best grand slam result came at Melbourne Park with a quarter-final berth in 2023.
Dial M for Murray: Novak Djokovic's coach Andy Murray watches the Serb eliminate Jiri Lehecka. (Lukas Coch/AAP PHOTOS)
While world No.29 Lehecka hit some spectacular winners, an unforced error tally of 44 cruelled his chances against the Serbian maestro.
Lehecka struggled to penetrate the game of the former world No.1, although he finally managed to break Djokovic's serve in the second game of the third set to level at 1-1.
That boost of confidence breathed life into the battle and, willed by the large crowd, Lehecka kept his nose in front as the set headed to a tie-breaker.
Djokovic took control early and gave himself two match points, wrapping it up at his first opportunity.
Jiri Lehecka was no match for 10-time champion Novak Djokovic, who won in straight sets. (James Ross/AAP PHOTOS)
Due to Djokovic's ranking dropping to No.7, the Tuesday night show-stopper against third-seeded Alcaraz comes earlier than many would deem worthy.
Last year, the pair squared off in the Olympic gold medal match, won by 37-year-old Djokovic, while Acalraz clinched their Wimbledon title showdown for the second straight year.
Alcaraz, 21, has won four majors and needs the Australian Open crown to complete his career slam.
His best result at the Open was last year's quarter-final showing, where he fell to current No.2 Alexander Zverev.
Djokovic exited in the semi-finals, beaten by eventual winner Jannik Sinner.
