It would seem the unlikeliest of friendships.

On so many levels, Andy Murray and Nick Kyrgios are simply different " often opposites.

One is an introvert, the other an extrovert.

One is among the sport's best defenders, the other wanting to be the aggressor.

One is mostly quiet, the other more expressive.

They do both mutter on-court " one mostly to his support team, the other to himself.

The duo shared Rod Laver Arena on Tuesday night, and Murray outclassed his 19-year-old opponent to reach the Australian Open semi-finals.

At the end, they shared words at the net " Kyrgios expressing his belief the Brit could go on to win his third grand slam.

"We've got a pretty good relationship. We've talked about it on Twitter," Kyrgios said afterwards.

"He's been a guy that's always been supporting me, so "

After his loss to Murray, Kyrgios tweeted: "Shame I couldn't get it done tonight but @andy_murray was just too good on the night.

"Muzza, I wish you all the best mate. #GoGetIt"

Murray had tweeted in June last year about the "next big Aussie star" after Kyrgios won the grass-court Challenger in Nottingham.

Just over a fortnight later, Kyrgios stunned the world by beating Rafael Nadal at Wimbledon.

Much has been made of Kyrgios' behaviour throughout his run at Melbourne Park, where he smashed racquets, swore for fun and questioned linespeople.

But Murray highlighted the Australian's sportsmanship, including giving opponents credit on-court.

"I actually think he's quite respectful on the court in many ways," he said.

"He does applaud good shots. He does say, 'Good shot, good serve.'

"Yeah, he gets frustrated with himself and sometimes says things he shouldn't, but everyone, I would think, has done that in some way when they're 19.

"It just happens that when he's doing it he's playing in front of a large audience and it gets picked up on.

"I've spent a little bit of time with him and I think he's a good person. I don't think he's a bad guy. He's nice. He's always been polite and respectful.

"Yeah, maybe he does the odd thing on the court that might annoy some people, but I don't think he does anything with bad intent.

"He's only going to continue to mature and improve in that respect as he gets older.

"He just needs to be allowed to grow up. Like everyone makes mistakes when they're that age."

There may be more linking the pair than first appears, however.

Kyrgios, like Murray certainly is, looks set to be the standout player of his generation in a nation which hosts one of the sport's four major tournaments.

Murray won Wimbledon at the eighth attempt after nearly a decade of intense scrutiny following him at the All England Club - Canberra's Kyrgios has just completed his first Australian Open run with a nation behind him.

With those shared experiences to lean on, Kyrgios has found himself an unlikely ally " one he should hold onto.