Nick Kyrgios triumphs over Herbert after umpire controversy

Umpire Mohamed Lahyani left his chair to speak to Kyrgios when the 30th seed was 6-4, 3-0 down to the Frenchman.

The full conversation was not audible but reports suggest that the umpire urged the player to try harder, saying, "I want to help you," and "This is not you."

Kyrgios, in response, suggested that he might call for the trainer and retire from the match.

Observers wondered whether such encouragement from an umpire was appropriate or permitted.

Kyrgios went on to win the second set - and the next two to wrap up the match 4-6, 7-6(6), 6-3, 6-0 and secure a third-round berth.

The US Tennis Association told reporters at Flushing Meadows that they were looking into the incident.

The US Open tournament referee Brian Earley later put out a statement explaining that the umpire left the chair "because of the noise level in the stadium during the changeover to make sure he could communicate effectively with Kyrgios," adding that he was "concerned that Kyrgios might need medical attention" and "that if he was feeling ill, that the tournament could provide medical help."

The statement also says that umpire Lahyani told Kyrgios "that if his seeming lack of interest in the match continued, that as the chair umpire, he would need to take action."