Rafael Nadal expressed his sadness at Andy Murray's impending retirement but backed the Scot's decision as the right move for his mental health.
A tearful Murray revealed on Friday that the pain in his hip has become too much to bear and the Australian Open could be his final tournament.
Nadal said: "Of course it's very bad news. But when somebody like him, he achieved almost everything in his tennis career, is suffering like he's doing for such a long time already, and you feel that you are not competitive for the thing that really makes you wake up every morning and go on court with the passion to practise, to improve, and with a goal, then it is so difficult.
"Probably he is fighting to keep going since a long time. If he doesn't feel that the thing can go better, probably he does the right thing for his mental health.
"It will be a very important loss for us, for the world of tennis, for the tour, for the fans, even for the rivals that he has been part of a great rivalry between the best players for a long time, and a great competitor. But that's life."
Few people would have put money on Murray being the first of the 'big four' to retire, and his imminent exit is a stark reminder that this golden generation cannot go on forever.
"It seems like he had not a very long career," said Nadal. "But he's 31. Ten years ago, if he retired at 31, we will say he had a great and very long career. We will miss him. But today it's him, tomorrow another one. We are not 20 any more. Our generation, everyone is more than 30."
Nadal was a junior rival of Murray and the pair have known each other for 20 years.
"When he was a kid, he was little bit a bad boy," said the Spaniard with a smile. "I always had a good relationship with him. We shared the court in the most important stadiums in the world, competing for the most important things. That's impossible to forget."