Pat Cash has launched a blistering attack on Nick Kyrgios, accusing his fellow Australian of cheating, abuse and dragging tennis down to new depths.

The 1987 Wimbledon champion, who commentated on Kyrgios's spiteful barn-burner of a victory over Stefanos Tsitsipas on Saturday, said the controversial Canberra showman was turning the game into a circus.

Both men were hit on Sunday for their dismal behaviour.

Tsitsipas was fined $US10,000 ($A14,700) for hitting a ball which narrowly missed spectators and Kyrgios, who'd already received the same punishment after spitting in his first-round match, was slugged a further $US4,000 ($A6,000) for his histrionics.

With Kyrgios given his first centre-court date of the championships on Monday in a fourth-round clash with American Brandon Nakashima, Cash said pointedly: 'Let's hope he doesn't drop tennis there to a lower level than he did on Saturday.'

Cash wasn't the only luminary to lambast Kyrgios, as Mats Wilander and even the greatest 'bad boy' of them all, John McEnroe, both weighed in.

In Saturday's contest, Tsitsipas could easily have been defaulted for whacking the ball into the crowd, and Kyrgios, who'd aimed foul-mouthed tirades at hapless chair umpire Damien Dumusois, tried to get the official to do just that.

The Greek, who twice also deliberately aimed to hit his opponent with the ball, claimed afterwards the Australian was a bully and had an 'evil side' while Kyrgios shrugged Tsitsipas was just soft and had 'serious issues'.

But Cash, in the BBC commentary box, was left disgusted by his compatriot.

'It was absolute mayhem,' he said on BBC radio on Sunday.

'He's brought tennis to the lowest level I can see as far as gamesmanship, cheating, manipulation, abuse, aggressive behaviour to umpires, to linesmen.

'He was lucky to even get through the first set, he should have been defaulted in the first set.

'Something's got to be done about it - it's just an absolute circus. Is it entertaining? Yeah, possibly. It's gone to the absolute limit now.'

Pressed on the cheating, Cash added: 'The gamesmanship. The abuse he was giving.

'Tsitsipas would make a line call and he'd go up there and start complaining, he'd be in his face - that's part of gamesmanship, that's the sort of stuff he does and I think there's a limit.

'I have no problems with a bit of gamesmanship but, when it gets to that level, I think it's just out of control.

'As it was, the umpire lost control. The ball kids were running across the court as Kyrgios was serving, he didn't slow down for any of that stuff.

'Tsitsipas got sucked right into it - so it was entertaining and fascinating, but for me it's gone too far now.'

Cash was speaking after he'd been on centre court for the centenary parade of former champions but he's evidently concerned at the prospect of how Kyrgios might conduct himself there.

Three-time Australian Open champion Wilander told Eurosport: 'I've never seen anything like it.

'I'm not sure I want to see something like that again, to be honest, because I don't think this is what we want to promote in tennis. We want to not promote it as entertainment.

'We want to promote it as inspirational, educational, but this is what people maybe want to see. I'm not sure I'm a big fan of what's going on to be honest.'

The greatest irony was McEnroe's attack while commentating for ESPN. 'It's embarrassing. He doesn't need to do all this,' said the man once dubbed 'Superbrat' at SW19 for his behaviour but is now one of its favourite fixtures.

'It's scary how good he is - that's what's sad in a way.'