NEW YORK • Roger Federer has said that umpire Mohamed Lahyani was wrong to get out of his chair at the US Open on Thursday to give Nick Kyrgios a controversial pep talk, which sparked a row over the impartiality of officials in the sport.

Lahyani stunned fans when he climbed down from his chair in the second set of Kyrgios' second-round match against Frenchman Pierre-Hugues Herbert on Court 17 to seemingly berate the Australian for a lack of effort.

"I want to help you. This isn't you. I know that. You are great for tennis," he could be heard saying.

Kyrgios went on to win 4-6, 7-6 (8-6), 6-3, 6-0, setting up a third-round clash with five-time US Open champion Federer today.

"It's not the umpire's role to go down from the chair," said Federer. "You don't go and speak like that, in my opinion. I don't care what he said but it was not just about, 'How are you feeling?'.

"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. I think everybody knows that."

At his news conference, Kyrgios played down the incident and the suggestion Lahyani had "coached" him through his struggles.

"It's ridiculous," said the 23-year-old. "He wasn't coaching me at all. What are you talking about?"

He added that similar conversations with chair umpires happened all the time.

And if Herbert had been on the receiving end of such a talk from Lahyani, he said, he would not have had a problem.

"He said he liked me," Kyrgios said. "I'm not sure if that was encouragement. He just said that it's not a good look."

Herbert said: "The umpire doesn't have to talk to him at all.

"The only thing he can tell him is pay attention, because if you continue like this, I'm going to give you a warning, something like this.

"He doesn't need to say the words he said on the video. I don't think he's a coach; he's an umpire and he should stay on his chair for that."

The US Open later released a statement saying that Lahyani had left his chair because he had wanted to be able to communicate effectively with Kyrgios in a noisy stadium.

According to the statement, Lahyani was concerned that Kyrgios might need medical attention and went on to inform him that he would need to take action if Kyrgios' "seeming lack of interest" in the match continued.

A couple of hours after his news conference, Herbert reacted angrily to the statement - a statement he said was "taking us for fools".

Richard Ings, a former umpires chief on the ATP, said Lahyani's move was unprecedented.

"I am racking my brain to think of a situation requiring a chair umpire to speak like that to one player," Ings tweeted. "I umpired thousands of matches (when) I was ATP head of officiating, I can't think of one."

However, former world No. 1 Novak Djokovic said that he believed there was nothing sinister in Lahyani's motives.

"Everybody who knows Mohamed knows he's quite different from others. He's always very positive, smiles, tries to bring that energy to the court," said the Serb.

"I really don't think that he meant to do it for any other reason but to really try to help Nick to understand that if he continues doing that, he might get fined or penalty or whatever, or warning."

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