A very serious allegation and the FA have a duty to look at it thoroughly. It could be career ending, aside from the fact that some young footballer may also need help in overcoming an addiction or mental issues.
The Sun should really now have to disclose its source to the FA for a full investigation, keeping names out of the public eye. It could well end up as nothing and the Sun inisting the reported it in good faith of the information given to them, but first and foremost is the realisation that maybe some young lad could need help here.