The Dutch ace fell out with the Scottish manager in the second-half of last season to the extent that Ferguson considered him a nuisance.

"I'm not so sure about Van Nistelrooy. That was not such a big decision at all," Ferguson told the Daily Star.

Ferguson said that what made it easy to release Van Nistelrooy was the fact that he negatively affected the team’s spirit.

"You need a good team spirit in the dressing room and from day one this group seemed to gel straight away. That was what I wanted.

"I kept referring to that through the season. The spirit was brilliant and that was important.

"We had to made big important decisions about how we change the team. That's not easy."

The 30-year-old Van Nistelrooy had no problem adapting to his new home at the Santiago Bernabeu and netting 20 goals so far in the strong Primera Liga.

Ferguson compared the Dutchman’s exit to that of former skipper Roy Keane.

"Well, Roy was certainly a difficult one," said Ferguson. "He has been such a big influence on the club."