Roger Federer believes Andy Murray will not want to defend his Wimbledon title if he is not fit enough to retain it.
World number one Murray has pulled out of an exhibition match on Friday due to a hip injury, having already withdrawn from a meeting with Frenchman Lucas Pouille on Tuesday because of the same problem.
As reigning SW19 champion, Murray is due to have the traditional honour of opening the championships on Centre Court on Monday afternoon.
But seven-time Wimbledon winner Federer warned: “I think he would need to feel like he could play for 14 days – or seven matches.
“If you feel you can only play one match, I don’t think then it’s good enough to play the tournament. Because going over the best of five sets, over two weeks, only the tough ones will survive.
“You need to feel confident in your body at some stage, otherwise what’s the point? To put yourself out there just to be out there? Andy’s had too much success to do that.
“The world’s watching because it’s the defending champion, opening the court, it’s a big deal.
“Because it’s a big deal you feel like you want to be at 100 per cent, or at least as close to 100 per cent as you can be.”
As well as his fitness worries, 30-year-old Scot Murray is desperately short of game time on grass having lost in the first round to Jordan Thompson at Queen’s Club last Tuesday.
It means the top seed will start the tournament without winning a match on the surface since beating Milos Raonic in last year’s final.
But Federer, favourite to land a record eighth Wimbledon title, still thinks that Murray – if fit – will be a major player at this year’s championships.
“He’s the reigning champ, so I feel for him the most important thing is to get through the first week, and the good thing for him is he’s a great first-week player,” added the Swiss star.
“He doesn’t mind the slippy grass, he doesn’t mind the bounce of the ball, he might even thrive in those conditions. So we will speak differently if he wins the first three matches.
“Regardless of how he played at Queen’s and how he is feeling now, if he is 100 per cent physically on Monday I think we will see a very strong Andy Murray at these championships.”
Federer was speaking at the unveiling of the Laver Cup trophy, alongside fellow tennis greats Rod Laver and John McEnroe. The inaugural Laver Cup, between Europe and the Rest of the World, takes place in Prague from September 22-24.
Greats of the game at Laver Cup launch: McEnroe, Laver and Federer.