Australian Open: Novak Djokovic congratulates Nadal 

Tennis star Novak Djokovic has congratulated the two Australian Open singles winners, Ash Barty and Rafael Nadal, after being denied the chance to compete for the title.

Nadal's gritty, five-set comeback victory over Daniil Medvedev earned him a record 21st major title, overtaking both Djokovic and Roger Federer who have both won 20 each.

"Congratulations to [Rafael Nadal] for 21st [grand slams]," Djokovic posted on his social media accounts.

"Amazing achievement. Always impressive fighting spirit that prevailed another time."

The Serbian also had some kind words for runner-up Medvedev, who he beat in last year's Australian Open men's singles final.

"[Medvedev] gave it his all out there and played with the passion and determination we have come to expect from him," Djokovic said.

"You put up one hell of a fight today and I know you will have more grand slam wins in your future."

Former world number one Roger Federer, the third of "the big three", also congratulated his "friend and great rival" in a social media post.

"A few months ago we were joking about both being on crutches. Amazing," Federer said.

"Never underestimate a great champion. Your incredible work ethic, dedication and fighting spirit are an inspiration to me and countless others around the world.

"I am proud to share this era with you and honoured to play a role in pushing you to achieve more, as you have done for me for the past 18 years."

In his first social media posts since leaving Australia, Djokovic also acknowledged Ash Barty, who also made history by becoming the first Australian woman in more than 40 years to win an Australian Open women's singles title.

"Congratulations to [Ash Barty] for an amazing performance in front of her home crowd and to Danielle Collins for an incredible tournament," Djokovic said.

Djokovic was deported on the eve of the Australian Open after his visa was cancelled and his appeals against that decision were dismissed.

Immigration Minister Alex Hawke used his ministerial powers to cancel the visa on "health and good order grounds", after concerns over Djokovic's stance on vaccination and information provided on his immigration forms.

After being detained at the airport, days of legal wrangling and two short stints in immigration detention, the Federal Court dismissed Djokovic's final application to have the cancellation decision overturned on January 16 and he left the country hours before the first round began.

Now-two-time-Australian Open champion Nadal said before the tournament began that he respected his Serbian rival "even if I [do] not agree with a lot of things that he did in the last couple of weeks".

"Honestly, I'm a little bit tired of the situation because I just believe that it's important to talk about our sport, about tennis," Nadal said.

The men's world number one remains at risk of missing the French Open too, with stricter COVID vaccination rules for entering sporting events on French soil coming into effect from February 15. 

Players are due to hit the Roland Garros courts on May 22