Rio Ferdinand has has said that Wayne Rooney was a very angry young man when he joined Manchester United.
Rooney joined United from Everton in 2004 to become the most expensive teenager in world football, but his initial attitude seemingly did little impress his new teammates.
Although Ferdinand revealed that Rooney did calm down later on in his career, he has suggested that the England star was difficult to deal with when he first arrived at Old Trafford.
"Wayne Rooney always struck me as a very angry young man, always arguing with people outside the training ground, especially on the phone," The Sun quote Ferdinand as saying in his upcoming autobiography.
"He seemed to fly into a rage about the smallest things and went through mobile phones like they were sweets. He’d smash phones up in frustration, throwing them on the concrete.
"I don’t know what happened but he did calm down."
Rooney's calming down off the pitch has been reflected by his more relaxed approach on it now, but there is a sense that this might have been where his career went wrong.
Of course, Rooney's conduct when away from the field apparently needed to be worked on, but it was this aggression when playing that made him such a sensation as a barrel-chested teenager.
When Rooney burst onto the scene his rawness and fiery temperament was his most eye-catching feature.
Never fearful of running at defenders, charging them down or giving them a physical contest, Rooney threatened to become one of the great players in world football.
Indeed, his performance at Euro 2004 for England remains his finest display at a major international tournament to date.
It is because of this that there is a question of what might have been with Rooney's career. His accolades and honours have shown how much quality he has, but the excitement he used to bring to the club appears to have disappeared somewhat.
The 28-year-old is on course to become United's and England's top scorer, but he may never go down as one of the greatest players to represent either side.
That was the path that Rooney has forged for himself as a teenager, but before he is 30 he is being surpassed by youngsters at both club and international level.
He is still clearly an extraordinary talent, but he is so refined on the pitch now that his greatest strength seems to have been coached out of him.
Rooney will forever have a place in the record books, but this calming down process which Ferdinand has revealed he went through during his career may just have stopped him fulfilling his ultimate potential as a player.