An umpire who gave a mid-match "pep talk" to Nick Kyrgios before he battled back to defeat Pierre-Hugues Herbert went "beyond protocol", US Open officials have said.
Australian Kyrgios was trailing 3-0 to the Frenchman in the second set of their match at Flushing Meadows on Thursday, but his fortunes changed after the bizarre intervention from chair umpire Mohamed Lahyani.
The US Open said a "comprehensive review" by multiple tournament officials found that Mohamed Lahyani's chat with the Australian player went "beyond protocol".
However, spokesman Chris Widmaier said the umpire would not be sanctioned on account of his "exemplary track record as an international tennis official".
The incident drew criticism from the tennis world, with stars questioning the talk.
Having appeared to be offering minimal effort to counter Herbert's powerful serve in the second round clash, Kyrgios was subjected to an animated dressing-down from the Swedish official as the players changed ends.
Television microphones were unable to pick up the entire exchange, but Lahyani was heard saying: "I want to help you, I know this is not you."
The 23-year-old star – who has drawn criticism for a similarly laissez-faire approach to his game on previous occasions – went on to win the second set 7-6, before comfortably seeing off Herbert 6-3 and 6-0 in the third and fourth.
It set up a third round clash with Swiss great Roger Federer, who is among the players to have criticised the umpire for his motivational chat.
Federer, who beat Frenchman Benoit Paire in straight sets in the second round, said: "It's not the umpire's role to go down from the chair.
"But I get what he was trying to do. He behaves the way he behaves.
"I don't know what he said. I don't care what he said.
"It was not just about 'how are you feeling? Oh, I'm not feeling so well.' Go back up to the chair. He was there for too long.
"It's a conversation. Conversations can change your mindset. It can be a physio, a doctor, an umpire for that matter.
"That's why it won't happen again. I think everybody knows that."
Herbert told reporters after the match that he was convinced the intervention had an impact on the result and said the umpire "should stay in his chair".
But despite criticism from fellow pros and outcry on social media, Kyrgios brushed off the incident in a tetchy exchange with journalists during his post-match press conference.
After sarcastically referring to Lahyani as "obviously an unbelievable tennis player", he said the pep talk "didn't help me at all" and said his opponent had "let me back into the second set".
Referee Brian Earley has issued a statement to explain what happened.
He said Lahyani left his chair to "check on the condition" of Kyrgios "because of the noise level in the stadium".
"Lahyani was concerned that Kyrgios might need medical attention," he added.
"Lahyani told Kyrgios that, if he was feeling ill, that the tournament could provide medical help.
"He also informed Kyrgios that if his seeming lack of interest in the match continued, as the chair umpire, he would need to take action."
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The Australian did receive treatment from his physio at the next break in play, at 4-1 down in the second set.
He will go up against Federer on Saturday.
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