I'm guessing if you can get round it using the editor, that's the only way. Because I'd never even heard of him until now, just done a quick search and I know Wikipedia isn't the trust-worthy source but apparently, according to his page Chelsea said in January he has never signed a contract, only appearing for the youth squad on trial. A contract might have been signed in the summer, but there's no mention of it on his Wikipedia page. But then, I don't understand why he'd be amongst the Chelsea players in the game if he'd never signed a contract.
Basically, what I'm saying is, I have no idea what you need to do in order for him to be able to play.