The Australian Open crowd was none too pleased with Novak Djokovic after an injury forced him out of his highly anticipated semifinal matchup against Alexander Zverev ... with spectators booing the hell outta the tennis legend as he walked off the court.
The injury -- a muscle tear that occurred in his quarterfinal victory against Carlos Alcaraz -- became too much for the 37-year-old to manage ... and after dropping the first set 7-6 (5) to the German star, he conceded the rest of the match.