Mike Phelan has revealed it was a challenge to transform Cristiano Ronaldo into a team player during his time at Manchester United.
Ronaldo became the most expensive teenager in English football history in 2003 when United paid £12.24million to secure his signature from Sporting Lisbon.
The Portuguese netted just four goals in his first Premier League season but soon developed into one of the most clinical forwards in world football.
He scooped the Premier League golden boot in 2008 before sealing a then world-record transfer to Real Madrid the following summer.
Phelan revealed that United coaches were keen to improve his teamwork during his spell at Old Trafford.
He believes the coaching methods worked, as Ronaldo went on to display the skills he picked up at Carrington while playing for Madrid.
"Ronaldo stood out," he told The Coaching Manual when discussing his time working with Sir Alex Ferguson.
"He was like a sponge. He wanted more [advice from United's coaches]. He challenged you for more.
"We had to try and get Cristiano to be a team player and he got it. In the end, he got it.
"There were certain things we did in training that made him do things he didn't want to do.
"Especially when the success came and after he moved to Real Madrid, there were certain things - when observing games at Madrid - that he definitely picked up at Manchester United.
"He was translating that further up the ladder of excellence. That's important and there's a satisfaction there.
"I don't claim to have created Cristiano Ronaldo. A lot of people have influenced him. But the biggest influence has been himself - his drive has been fantastic."