Roger Federer says Andy Murray is a "legend" and the game's top players will be "hit hard" by his retirement.
Murray revealed on Friday he is still troubled by the hip injury that has plagued him for the last 18 months and he plans to retire after Wimbledon in the summer.
He also admitted the Australian Open which begins on Monday may be his last tournament.
The 31-year-old was the first British man to win Wimbledon in 77 years and will be remembered for battling his way to world No 1 in 2016 during a golden era for men's tennis alongside Federer, Novak Djokovic and Rafael Nadal.
"I was disappointed and sad, a little bit shocked, to know now that we're going to lose him at some point," Federer said on the eve of the year's first Grand Slam.
"But we're going to lose everybody at some point. It's just now that it's definite," he added, acknowledging the era of the "Big Four" - himself, Djokovic, Nadal and Murray - was drawing to a close.
"Of course, it hits us top guys hard because we know Andy very well. We like him. He doesn't have many enemies, to be quite honest.
"He's a good guy, Hall of Famer, legend. He won everything he wanted to win. Anybody would substitute their career with his. He's a great guy."
Murray has won Wimbledon twice during his career and Federer is hoping the three-time Grand Slam champion can play long enough to say goodbye on the grass courts where the Swiss has won a record eight titles.
"Of course, I hope that he can play a good Australian Open and he can keep playing beyond that, really finish the way he wants to at Wimbledon," Federer added.
"That's what I hope for him. It's a tough one, but one down the road he can look back on and be incredibly proud of everything he has achieved."
Federer begins his Australian Open title defence on Monday against Denis Istomin.
Murray faces a first-round match against in-form Spaniard Roberto Bautista Agut, who beat Djokovic on his way to winning the Qatar Open earlier this month.
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