Nick Kyrgios takes a nap during US Open loss to Andy Murray

The Australian bad boy found himself in hot water last month, after a series of controversial incidents, including sledging Stan Wawrinka at the Montreal Masters.

During the 7-5 6-3 4-6 6-1 defeat to Murray, Kyrgios produced moments of pure brilliance that had the Arthur Ashe Stadium crowd applauding.

It was all part of a bizarre display that saw the enigmatic Kyrgios entertain and infuriate in equal measure, nonchalantly walking up to take routine overhead smashes and stretching out in his chair for a quick nap between changeovers.

"Just taking a nap, I guess. It's good for you," shrugged Kyrgios after the match. "I've always been an emotional person on the court. And, yeah, I like going for shots that aren't high percentage.

"I just got a really good self-confidence."

Already fined and under scrutiny from ATP Tour officials for ugly comments directed at Wawrinka, Kyrgios's antics will not have helped polish his tarnished reputation.

Kyrgios sparked outrage at the Rogers Cup when a courtside microphone picked up the Australian's lewd remarks towards his Swiss opponent concerning the French Open champion's private life.

The 20-year-old has been on a damage limitation drive ever since and has not won a match.

Kyrgios kept his trash-talking in check against Murray but that seemed to be the only part of his game under control as his focus and effort fluctuated from point to point.

Before play began, Kyrgios set the mood by turning to the stands behind him and staring down late arriving spectators.

Just five points into the match, he was already muttering to himself and hammering at balls in frustration.

Watching from the players' box was Australian former world number one Lleyton Hewitt, who has taken on the role of Kyrgios' mentor.

A former US Open champion who played every ball as if it were championship point, Hewitt admitted he has a very different type of game to Kyrgios but believes there is still plenty he can teach his compatriot.

"I do feel for him," said Hewitt, who is pulling double duty at Flushing Meadows as mentor and player, advancing to the second round with a 6-0 7-6(2) 1-0 win over Aleksandr Nedovyesov.

"He's a good kid," he added. "Just trying to work through certain things more on court than anything."