MELBOURNE: In drawing level with Rafael Nadal's record 22 Grand Slam titles, Novak Djokovic reignited the debate about who is the greatest men's tennis player of all time.For some, the Serb settled it with his record-extending 10th Australian Open crown.Certainly his vanquished opponent on Rod Laver Arena thinks so."He's the greatest that has ever held a tennis racquet, for sure," said Stefanos Tsitsipas after losing 6-3, 7-6 (7/4), 7-6 (7/5).It seems inevitable that Djokovic, who returned to world number one with his dominant victory in Sunday's final, will win more Slams.At 35 he is a year younger than great rival Nadal and except for hamstring trouble early on in Melbourne, he appears to be in excellent physical shape.In contrast, Nadal's battered body broke down again at the Australian Open and he limped out with defeat in the second round, his title defence over and the Spaniard in pain with a hip injury.Roger Federer, the third of the "Big Three" who have dominated men's tennis for the past 15 years, retired last year with 20 Grand Slam titles.Federer will always be the "people's champion" in the eyes of many because of the graceful way he played, but it is Djokovic who looks primed to pull away with the record number of men's major crowns.Djokovic seems to thrive on pain and feed off adversity.Two years ago he won in Australia despite tearing stomach muscles, this year it was a hamstring that did not allow him to practise between matches.If not for Djokovic's COVID-19 vaccine status, which saw him deported from Australia a year ago and prevented him competing at the US Open, he may well have already been on 23 or 24 Slam wins."Haha, I told you.