Nick Kyrgios could be heavily sanctioned by the ATP after he verbally abused the chair umpire and then appeared to spit in his direction at the conclusion of his second-round exit from the Cincinnati Masters.
The 24-year-old Australian overcame a calf concern and a 5-2 deficit to take the first set, before his mental demons took control during the 7-6 (7-4) 6-7 (4-7) 6-2 loss to the Russian eighth seed Karen Khachanov.
Kyrgios took umbrage with umpire Fergus Murphy, who he has previous history with, over his monitoring of the shot clock and berated the Irishman for most of the match.
He became obsessed with the issue, repeatedly calling Murphy a "potato" and labelling him a "disgrace" and the "worst ref in the world".
Murphy eventually responded by handing Kyrgios a point violation after Khachanov won the second-set tiebreaker to level the match, when the Canberran overstepped the mark by screaming out an obscenity.
Kyrgios then followed this up by asking for a toilet break. He took two racquets with him and smashed them in the players' tunnel before returning to the court.
While Kyrgios was still capable, wowing the crowd with the occasional winner in the third set, his focus was gone and he conceded a break in the sixth game by attempting a tweener drop volley.
After a double-fault handed Khachanov the match and the players shook hands, Kyrgios told Murphy "you're a f***ing tool bro" and appeared to spit in the direction of the umpire before he shunned the traditional handshake.
Ranked 27th, Kyrgios still appears likely to be seeded for the season's final Grand Slam starting in New York on August 26.
But the temperamental star may face significant fines for smashing two racquets in the vicinity of the court, verbally abusing Murphy, and not actually using the bathroom after requesting a toilet break.
Khachanov will play Frenchman Lucas Pouille next, with the winner likely to face off against top-seeded titleholder Novak Djokovic in the quarter-finals.