Since Christiano Ronaldo wants to leave United, I think he wants to meet new challenge because in Premiereship nobody can stop him. Maybe in La Liga with Real Madrid he can find the real challenge so he can explore his skills. Beside, why United still hold him when they know if Ronaldo's heart is already not in United anymore? If United let Ronaldo go to Madrid they will get high profit from this transfer because Madrid is willing to pay more than about 80 million euro. So just let CR7 leave United.