Ruud van Nistelrooy said the breakdown of his relationship with manager Sir Alex Ferguson was the only reason he wanted to leave Manchester United.
Van Nistelrooy insisted he would not bear a grudge against Ferguson
"My relationship with Ferguson had ended which was very painful," said the 30-year-old Dutchman after signing for Real Madrid on Friday.
"It had nothing to do with the club or the fans.
"It was the relationship with the manager that broke. I thought it was best to leave."
Van Nistelrooy said he had begun to feel unsettled at Old Trafford after he was left out of the team for February's Carling Cup final.
He eventually handed in a written transfer request, with Real Madrid seeing off competition from Bayern Munich for his signature.
Ferguson did a lot for me, waiting for me while I was injured
However, Van Nistelrooy said he did not bear a grudge against Ferguson over the bitter end to his five-year spell at United.
"I had an incredible five years in Manchester and I will always remember my time there and the unconditional support from the fans," he said.
"I never got to say goodbye to Ferguson but there is plenty of time for that. I owe him a lot and that is why it was so painful."
Ferguson pressed ahead with a move for Van Nistelrooy even after the then-PSV striker failed a medical in April 2000.
The Dutchman then sustained a serious knee injury while training with PSV a few days later but United stood by him and he eventually joined for £19m.
"Ferguson did a lot for me, waiting for me while I was injured then giving me the chance to play and giving me confidence," Van Nistelrooy told a news conference at the Bernabeu on Friday.
"But what happened, happened. A good relationship ended. It was very disappointing for me."
United issued a statement on their official website, which read: "Manchester United would like to wish Ruud all the best at his new club and thank him for the great service he provided."