Tennis star Nick Kyrgios has proved his rivalry with Stefanos Tsitipas is alive and well by slamming the Australian Open finalist in a vicious tweet on Sunday.

Kyrgios and the world No.3 had a famous clash at Wimbledon last year with both players fined after the Greek smashed a ball into the crowd and branded his opponent an 'evil bully'.

The Australian was reacting to a tweet quoting Tsitsipas as saying: 'He was the one who broke our relationship. I didn't do anything. In 2022 Wimbledon I was only trying to compete, while he was playing the clown.'

Kyrgios responded by tweeting: 'Right..... this the match where he hit someone in the crowd..... belted another ball out of the stadium and got taught a lesson in front of another full stadium.'

The match was won by the Australian, who went on to lose to Novak Djokovic in the men's singles final.

On Sunday, Tsitsipas also said, 'I was just trying to play and someone on the other side of the net was looking for trouble, doing his antics. It depends on which foot he wakes up with every day.'

He also described Kyrgios - who at one point called for a supervisor and refused to play during the pair's Wimbledon clash - as a 'devil when he enters the court'.

Fans who were hoping to see the pair clash at last month's Australian Open were left bitterly disappointed when Kyrgios was forced to pull out in order to have surgery on his injured left knee.

More drama followed for the 27-year-old last Friday, when he pleaded guilty to assaulting his ex-girlfriend Chiara Passari in 2021.

The tennis star fronted the ACT Magistrates Court in Canberra, where a bid to have the assault charge thrown out on mental health grounds was rejected.

But magistrate Beth Campbell threw out the charge, accepting the seriousness of the matter was 'low-level' and indicating Kyrgios was not a risk of reoffending.

The Wimbledon finalist had admitted assaulting Passari by pushing her to the ground after a heated argument. 

Kyrgios said he was 'not in a good place' at the time, and that he 'reacted to a difficult situation in a way I deeply regret'.

'I respect today's ruling and I'm grateful to the court for dismissing the charges without conviction,' he said in a statement. 'I was not in a good place when this happened and I reacted to a difficult situation in a way I deeply regret.

'I know it wasn't OK and I'm sincerely sorry for the hurt I caused.

'Mental health is tough. Life can seem overwhelming. But I've found that getting help and working on myself has allowed me to feel better and to be better.'

Kyrigos finished the statement with a message to his supporters.

'I can never thank Costeen, my family and friends enough for supporting me through this process,' he said. 'I now plan to focus on recovering from injury and moving forward in the best way possible.'