The much-troubled 35-year-old told The Mirror: "I've had physical tests and I am confident that I will come back faster, stronger and fitter than I ever was.
"A month from today I guarantee I will be able to stand side by side with any striker in the country and my physique will be up there with any of them.
"This time I'm not going to self destruct. You are not going to see headlines about me being kicked out of a bar somewhere in the early hours rolling drunk.
"The sports scientists who conducted the tests said I had the fitness levels of an elite athlete. They said I was like a car with a six-litre engine, not your Joe Bloggs three-litre model."