Nick Kyrgios was involved in more controversy at the US Open after appearing to benefit from a pep talk from umpire Mohamed Lahyani during a four-set victory over Pierre-Hugues Herbert.
Trailing by a set and 2-0 in their second-round clash, Kyrgios barely attempted to return serve during the next game and sat disconsolately down in his chair to the sound of booing from the crowd.
At which point Lahyani came down from his chair, an unusual move, apparently to urge Kyrgios to show more effort, and could be heard telling him: "I want to help you. You are great for tennis. I know this is not you."
There was an immediate reaction from current and former players on social media claiming Lahyani had majorly overstepped his role.
Kyrgios held serve in the following game and then broke the Herbert serve four games later to keep the set alive before clinching the tie-break and going on to win 4-6 7-6 (8/6) 6-3 6-0 victory.
The Australian played down the effect of Lahyani's intervention, claiming it was no different to previous chats he has had with umpires when he has not been appearing to show his best effort - a sanctionable offence.
Kyrgios said: "I'm not sure it was encouragement. He said he liked me. He just said that it's not a good look. I wasn't feeling good. I know what I was doing out there wasn't good. I wasn't really listening to him, but I knew it wasn't a good look.
"It didn't help me at all. I was down 5-2. If it was 3-0 and maybe if I would have come back and won six games in a row, fair enough. It didn't help me at all."
Kyrgios described suggestions Lahyani could have been construed to be coaching him as "ridiculous" and added that he hoped the umpire would not face any sanction.
Kyrgios, meanwhile, twice bit back on Twitter at fellow player Donna Vekic for questioning Lahyani's conduct but deleted both messages and later apologised.
Vekic's boyfriend Stan Wawrinka then joined in, posting a picture on Twitter accompanied by the hashtag #shhh.
Unsurprisingly, Herbert had a different take on the situation, especially after seeing the conversation on TV.
The Frenchman said: "On court I tried to focus on myself. I just saw that Mohamed went down at the chair. I was a little bit surprised. I didn't listen to what they said. I just saw that Nick from that point started to play really focused, 100 per cent. Then I saw what happened after the match.
"First of all, I'm upset against me because I should have finished the second set. You never know what would have happened if Mohamed didn't go down off the chair and started talking to him.
"He can tell him from the chair. He doesn't need to say the words he said on the video. I think this was not his job. I don't think he has to go down and take the position of a coach, like you see on the WTA Tour. I don't think this is appropriate for an umpire to go down and say, 'I want to help you'."
Herbert was preparing to talk to Lahyani and expressed a wish for him to face a fine or similar, but that seemed unlikely to happen after tournament referee Brian Earley released a statement essentially supporting the umpire, citing the noise in the stadium for him getting off his chair to talk to Kyrgios.
The United States Tennis Association, which runs the tournament, continued to investigate, and in the meantime Herbert responded to Earley's statement on Twitter, accusing the USTA of "taking us for fools".
He said: "I am even more upset against the statement of the USTA that is clearly taking us for fools. We all hear on the video what the umpire said to Nick overpassing (overstepping) his functions. (To) err is human but I still wait for explanations. When we players are making mistakes on court we are sanctioned."
Next up, the Australian faces second seed Roger Federer in a crowd-pleasing third-round clash. Federer was tested by Frenchman Benoit Paire but did not drop a set in a 7-5 6-4 6-4 victory.
Asked how he would respond if the umpire in the next match does the same thing as Lahyani, Federer said: "That won't happen. It's not the umpire's role to go down from the chair. You don't go and speak like that in my opinion. He was there for too long. Conversations can change your mindset."
Kyrgios and Federer have met three times before, all in best-of-three-set matches, each of which went to a deciding tie-break, with Federer leading 2-1.
Kyrgios said: "For sure, to win three sets off Federer you have to play some pretty consistent tennis. But he's never played me in best of five either."