Dominic Thiem insists Novak Djokovic must be regarded as the greatest tennis player of all time, ruling Roger Federer and Rafael Nadal out of contention.

Despite a hamstring issue, Djokovic became the joint-most successful male player in grand slam history last week as he moved level with Nadal on 22 titles following his record-extending 10th Australian Open triumph.

Along with retired 20-time major winner Federer, Djokovic and Nadal find themselves in the long-running debate to determine the greatest player in history.

But 2020 US Open champion Thiem, who believes the number of major wins must be the decisive factor in the conversation, is confident Djokovic will soon leave his two great rivals firmly behind.

"In my opinion, the grand slam titles should be the defining criteria when determining the best of all time, they are the four most important tournaments in tennis," the Austrian said.

"Everything else is fine, but it's not the same. The slams are what counts, so the GOAT will probably be the one with the most grand slams.

"I am not very surprised [by Djokovic's Melbourne triumph]. Djokovic still looks young – physically and mentally, because of the way he moves on the court. It's like he was 25 years old.

"We have to be honest, he is the best, so his victory was not very surprising."