Robbie Williams has injured his back jumping from a roof
The `Angels` hitmaker wants to get back in shape ahead of the Soccer Aid charity tournament - in which he will captain an England team of celebrities and former players against a Rest of the World side, led by actor Michael Sheen - but is worried he has jeopardised his chances after an attempt to prove his athleticism went wrong.
He wrote on his blog: "I`m watching you Michael Sheen! Your next role better be `My Left Foot Two` `cos that`s all you`ll be able to play after I`ve finished with you.
"Having said that, I`ve got to fix my back. I jumped off the studio roof a week ago `to see if I still could` - evidently I can`t...
"Lesson learnt; when you stop jumping over things to see if you can, leave it."
Robbie recently set up a poker website to play online with fans and admits the game is beginning to "take over" his life, though he is enjoying getting the chance to bond with his devotees.
He wrote on his blog: "FunPoker is mental! Amazing banter, genuinely laughing out loud with you all, you funny f**kers.
"It`s taken over my life right now. Thank God I`m not recording at the moment, I`d get nothing done.
"I always wanted a game to play with you all. I suggested backgammon a while ago but this is perfect."
Other celebrities confirmed to be taking part in Soccer Aid, which returns after a two-year break on May 27, include chef Gordon Ramsay, Marvin Humes and Aston Merrygold from JLS and former soccer stars Teddy Sheringham and Edwin van de Sar.
Money raised from ticket sales and donations will go to UNICEF.
The tournament has previously raised over ё7 million for the organisation since the first game was staged in 2008.
Tickets for Soccer Aid - which takes place at Old Trafford in Manchester - are on sale now.