After Nick Kyrgios was involved in yet another clash with an umpire during his surprise first-round defeat at the Shanghai Masters, Roger Federer warned that the Australian may never reach his full potential.
The fiery 23-year-old Aussie was upset with umpire Damien Dumusois, who deemed his effort "borderline" after it appeared Kyrgios tanked on a return of serve in the second set.
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From then on, Kyrgios, who recently lost his place as Australian No. 1 to 19-year-old Alex de Minaur, made a point of turning to Dumusois and saying "borderline" every time he hit an unreturnable serve past opponent Bradley Klahn.
"I think it's really up to him where he wants to go and what his potential really holds," said Federer, who is the defending champion in Shanghai.
"We don't really know and I don't think he really knows exactly what his potential is.
"And only through understanding work ethic and scheduling and whatever it might be, creating the right team around himself, only then can you unlock the potential really."
It's the third time in as many years that Kygrios' elimination from the Shanghai Masters has been mired in controversy.
Last year the 23-year-old was fined $10,000 for unsportsmanlike conduct after he walked off midway through his first-round match against Steve Johnson, while in 2016 he received another fine and was suspended for eight weeks from the ATP Tour for tanking.
Despite his latest outburst, Kyrgios still received the backing of 20-time major winner Federer to "win bigger tournaments."
"But there is still a process in place that he needs to do like any other player needs to go through in order to be successful," he said.
Following recent incidents at the US Open, one of them involving Kyrgios, umpires now find themselves under an increased level of scrutiny.
Mohamed Lahyani, a vastly experienced chair umpire, was banned from two tournaments after it was deemed he went "beyond protocol" for encouraging Kyrgios during his victory over Pierre-Hugues Herbert.
The China Open, which finished Sunday, and the ongoing Shanghai Masters were the two tournaments the Swede was suspended for.
At the US Open, Lahyani was heard telling Kygrios "I want to help you" during a changeover as he trailed his French opponent, before the Australian rallied to win in four sets.
During Monday's defeat, Kyrgios threatened to go to the ATP offices after the match and report Dumusois, saying he felt "put down" by his comment.
"You'd be in trouble, right?" he said. "I'll literally just say I couldn't play after that because I felt put down. You realize that, right? I'm not going to do it, but I'm just saying."
Dumusois replied: "You can do it if you want, if you feel like doing it. If you say so and you believe it's the case, you should do it. I'm honest in saying that."
Following the fallout from the US Open, top umpires were reportedly considering forming a union as they believed Ramos was not offered enough support and was "hung out to dry."