The Angels hitmaker, who was among those who first came up with the idea for the charity kick-about, reveals he's keen to play but he can't get insured.
He explains, "I’m in the middle of a tour. We just came in from Zurich and if I do the back in out on the pitch, the tour goes kaput and I’ll have to sell either (wife) Ayda or (daughter) Teddy. And I’ll miss Ayda."
He adds, "I’ve got two discs rubbing together on my back... My body is knackered, but the spirit is still the same and the reason why I’m here is still the same."
Williams won't be absent from the big game at Old Trafford on Sunday (08Jun14) - he'll help West Ham United boss Sam Allardyce manage the England Xi as they take on Gordon Ramsay and James MCAvoy's Rest of the World team.
The annual match raises funds for Unicef, of which Williams is an ambassador.