The 31-year-old left United for Fulham on transfer deadline day.
"I don't think I deserved such treatment at United - not playing in the last year," Berbatov told reporters.
"I went more than 10, probably 15, times to ask the coach if they need me. And every time I was told that I'm an important player and should not leave, but then again I was not in the team.
"Maybe I should've gone when he [Ferguson] left me out of the squad for the Champions League final. I know he's the boss, but he has lost, to some extent, my respect because of the way he treated me."
"He [Ferguson] tried to explain to me that the team will be using a more direct style, with more speed," he added. "But I've never been among the fastest players, I like to hold the ball, this is my style.
"I found it hard to accept his decision - I still have my dignity. I scored many goals, I won the league two times, and I was the league top scorer, so it's not bad.
"I'll have no problems playing against United as this already happened in my career. But there's no point to look back again. I said goodbye to the people, who deserve it. I couldn't say goodbye to Ferguson."