Stan Wawrinka says Rafael Nadal cannot be compared with anyone else in tennis following his achievements.
Nadal won his 21st major title at the Australian Open, made all the more remarkable by the fact he was coming back from a serious foot injury.
But Wawrinka - himself on his way back to the tour after a long injury absence - said he wasn't surprised by what Nadal managed to accomplish in Melbourne.
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Speaking on L'Equipe's Air Open podcast, the Swiss star said: "Whatever happens we cannot compare Nadal with other tennis players, that's for sure.
"Nadal has been out for four, five or six months almost every two years of his career, and whether the injuries were serious or not, he always managed to come back.
“And once again at this stage and level, with the difficult last year that he had, of course, it’s exceptional, just like all his career.
“Sometimes, I feel, tennis is all written in advance. Before Australian Open I was talking to my coach, Dani [Vallverdu] and we discussed that Nadal will win Australian Open, because everything is written.
"He was doubtful but he’s an exceptional champion. He has 21 Grand Slams, let's see if others and Novak [Djokovic] will win more or not.
"It was brilliant to watch his win. I wasn't surprised but I admire that he is still able to do it and as I say I am not surprised because we know that he is well above everyone else. He's proved that he's able to do things throughout his career that others can't.
“We saw what happened to Nadal last year, a year full of injuries and it would have been impossible to say he will win Australian Open last year. But his win is a bit similar to that Federer’s in 2017 and he has written history.”

Watch historic moment Nadal wins Australian Open and claims 21st Grand Slam title

Wawrinka revealed recently that he is targeting the French Open for his return to competitive action.
He said: “People often ask me why I’m trying to come back after my injury and carry on, but it’s because I’m passionate about tennis, I love the spectators.
"When I walk out on court, I make sure I remember that it’s a game. The whole basis of tennis is that we tell children to 'go and play'! A lot of people forget that when they turn professional: they see tennis as a job.
"What motivates me the most is reminding myself that I’m going to play, have fun and enjoy myself.”
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