Sir Alex Ferguson has branded Ravel Morrison's failed time at Manchester United as the "saddest case" he dealt with.
Morrison was one of English football's hottest prospects during his time at Old Trafford, but issues of the pitch prevented him from fulfilling his potential.
The 22-year-old, now with Lazio, admits that United gave him "too many" chances before he left the club back in 2012.
But his manager of that time, Ferguson, revealed that he tried to show faith in Morrison at United - and was extremely disappointed when it did not work out for him.
Writing in his latest book, Leading , Ferguson said: "Sadly, there are examples of players who have similar backgrounds to Giggs or Cristiano Ronaldo, who, despite enormous talent, just aren't emotionally or mentally strong enough to overcome the hurts of their childhood and their inner demons.
"Ravel Morrison might be the saddest case. He possessed as much natural talent as any youngster we ever signed, but kept getting into trouble.
"It was very painful to sell him to West Ham in 2012 because he could have been a fantastic player. But, over a period of years, the problems off the pitch continued to escalate and we had little option but to cut the cord."
Morrison is currently playing for Lazio in Serie A after moving from West Ham earlier this year.
He has made only two appearances in the league, both from the bench, and has already been tipped for a move back to England with QPR.