The Australian led two sets to love against Italian Andreas Seppi before losing the next three sets to bomb out of his home grand slam.

The 21-year-old seemed in total control during the opening exchanges but lost his temper and his way to be booed by his home crowd after losing the fifth set 10-8.

McEnroe, who has been critical of Kyrgios in the past, said the Aussie was a “black eye for the sport”.

 “Even I’m at a loss for words,” said McEnroe, commentating for Eurosport. “Overall I would call it a damn shame because I think he’s the most talented guy in the world (aged) 21 and under — maybe even at 29 and under.

“He could be the best player in the world, but mentally he’s No. 200 in the world, and I think at critical moments it showed.”

“It’s OK to show your emotions, and I’d like to see that in a one-on-one game when you’re out there by yourself,” McEnroe added. “But when he goes through those periods when he’s not competing, then it’s just a black eye for the sport. And it’s a black eye for him.”

Kyrgios praised Seppi’s fight adding it was hard to cop boos from fellow Australians.  

“It’s obviously disappointing. But, you know, it was ultimately a pretty fun match,” he said.

“He’s a great guy and he deserved it, so I’m not going to beat myself up about it.

“Yes, obviously it’s not the greatest thing to hear (booing at the end). I didn’t have the best preparation coming into the Australian Open. Pretty banged up, my body.

“You know, I don’t even know what the score was in the end. Was it 10-8? 10-8 in the fifth, getting booed off, definitely not the best feeling.”