#3 Ro-Shaun Williams
Ro-Shaun Williams is a little bit older than the rest of this list and is a centre-back by trade. He entered U23 football at a very young age, and he did that because he was already developed mentally and physically. He shows incredible character and is a genuine leader which is rare in these modern times.
Whilst most players are timid, quiet and selfish, Williams will do everything for the team, whether it be through sheer encouragement or putting his body on the line to stop a goal, he does it all. He's also surprisingly fast for a player of his stature and he posses a good ability on the ball. Williams is also good in the air, so he has all the traits to be a brilliant defender in the future.
All Williams needs is a chance and with a complete lack of centre-backs available and question marks over the long-term quality of the centre-backs currently present at Manchester United, Williams should already be getting in and around the senior squad and having bench time if not getting minutes late in games.