West Ham boss Sam Allardyce believes he signed a boy in Ravel Morrison but that the midfielder will return to Old Trafford on Saturday as a man.
The 20-year-old was a product of United's fabled youth system but appeared just three times for the Red Devils before joining the Hammers in January 2012.
England U-21 international Morrison is West Ham's top goalscorer this season with five and Allardyce feels the player has developed so much that he will be completely different when he lines up against United for the first time on Saturday.
England Under-21s forward Ravel Morrison
Ahead of Saturday afternoon’s Premier League meeting between the two sides, Allardyce said: "Sir Alex [Ferguson] let Ravel go for his own benefit.
"He said that if he comes down to you hopefully he will find a new life and a new way of living.
"His ability will then start to come through because all he asks and all he wants in his life is to play first-team football, that was all he said he wanted to do and why he wanted to leave.”
He added: "In actual fact he struggled to look like he was capable of playing football in the first team with us. That's why we sent him on loan to Birmingham and I thought since that year he's grown up.
"Somewhere along the line the lad has woken up and I think he's changed himself and delivered."
Ravel Morrison in action against Lithuania
Morrison has been a shining light in West Ham’s season so far, but Allardyce is keen to keep him focused and unlock the match-winning potential as often as possible, with a warning that he should not try and steal the show against his former club.
Allardyce said: "The expectation becomes “will it come every single week" and that can't really happen at such a young age.
"It's nice if it does. We've got to manage the situation and just try and keep encouraging him.
"I think from our point of view, if he gets selected for Old Trafford on Saturday, that the real message from me to him would be to try and get a result as a team and play one of your top performances in a team situation when you would help to get us that result buy using your abilities in a team performance.
"When you've got his ability there is going to be the temptation to go out and show "look at me" I think and I have to try and guard and avoid that situation."
