John McEnroe called it "beyond belief", Tim Henman declared it "shot of the year" while Nick Kyrgios's mum said it was "a bit cheeky".

Every person in Wimbledon's Centre Court applauded in awe.

Australian teenager Kyrgios's audacious between-the-legs winner in his fourth-round win over Rafael Nadal went viral on social media and is the talk of the tennis world.

With scores locked at 3-3 in the second set, 19-year-old Kyrgios played a shot most in his position would never dare try, let alone pull off.

A powerful Nadal backhand was struck straight at the Australian, who duly opened his legs and clipped an outrageous winner just over the net.

Kyrgios tried a few other other "tweeners" in his previous matches at the All England club this week.

This one, at a moment of tension against the world No 1, stuck.

Backing up in the early hours of Thursday morning in a quarter-final against Canadian Milos Raonic, Kyrgios raised his arms and circled for the crowd, as if to say "You're welcome".

Nadal, in no mood to admire, turned his back almost immediately.

The shot drew comparisons with Roger Federer's famous "tweener" at the 2009 US Open, considered by some as the greatest shots of all time played.

In the context of the match, Kyrgios's winner meant little.

He was 40-0 down at the time and went on to lose the game and the set.

However, it was a perfect illustration of the fearless attitude that helped him pull off one of the biggest upsets in grand slam history.

It was one of a stack of winners for Kyrgios, who said his aggressive shot making is more than a case of youthful exuberance.

"I love to entertain. I think I'm always going to have a style of game that's aggressive," he said. AAP