He continues:
"Unfortunately, although the lad might not see it now, he'll be 40 one day and he'll be unhappy with himself because he didn't give it everything he should have done.
"Once that time has gone, it's gone forever and, take it from one who knows, the best days of any footballer's life are when you are playing.
"He'll regret it one day and he'll have to live with that.
"You don't just lose the ability he possesses overnight, but it's all gone wrong.
"It's frustrating to watch because when we do fitness tests on him he's up there with the best - but, sadly, there's no test you can do on his head to make him fully focused.
"He's a class performer, but that's not all the game is about. He has wonderful talent - but that's only part of being a good player.
"Dwight is fit but I haven't brought him to Germany with the rest of the squad.
"What's the point? I have Jon Stead, Andy Cole, Matt Jansen, Paul Dickov and Paul Gallagher - that's five strikers.
"People may look at that and make their own judgements on Dwight and his future here. Football is a strange business and plenty of funny things happen.
"I have been around long enough to never say never, but he is now sixth choice as we stand today - and that's the reality of the situation."