Heinze told the News of the World: "I deserved better treatment after my efforts for the club.
"I had to leave United because I am convinced Ferguson would not give me a minute all season.
"I thank the United fans - but they are very different to the directors."
He believes Fergie held a grudge against him the moment the Argentina defender appeared in last summer's World Cup in Germany.
Heinze said: "My relations with him were normal until my bad knee injury in September 2005 and my efforts to play in the World Cup at the end of that season.
"I went to Spain for recovery but Ferguson thought it would be impossible for me to play in Germany in the proper condition.
"You could say I won the bet but I upset him and from that moment on, things were different between us."
He added: "The rivalry between United and Liverpool is fuelled not by sporting matters but by a hatred between the clubs.
"For Ferguson this was a personal question and he never wanted my transfer to up the road to Liverpool.
"But if I had to leave United it had to be for a big club in Europe.
"Real are the champions of Spain and one of the biggest teams in the world.
"Anyone would want to play for them."