The clue here is whether as a player they have shown the ability to max out on the natural footballing ability that they were born with. Jackie Charlton, great manager, absolutely made the best of what he had been given as a player. Bobby Charlton not so good as a manager-super players sometimes struggle to understand why lesser mortals can't do what they can. Good managers of the future also have to show leadership on the pitch.
I would have gone for Godden too but he is obviously smart enough to build another career. McFadzean is the one that appears to fit the bill.
Incidentally I would have tipped Rooney to do well, because under Fergie he was smart enough to curb the individualism he had shown at Everton and also curb his ego, to play for the team as instructed. Shows he was not stupid, like a lot of big stars.
Doyler is the answer to the question though.