Nick Kyrgios is out of the Australian Open -- the tennis star officially withdrew from the high-profile tourney ... after he had some disgusting, ketchup-like fluid drained from his knee.
The 27-year-old called a press conference at Melbourne Park on Sunday to reveal the news ... announcing that a recent MRI scan showed he had a small tear and cyst in his lateral meniscus.
He shared on his IG story shortly before the announcement that the injury had led to a buildup of a gnarly substance in his knee that required a procedure to remove.