The 31-year-old, who joined Fulham on transfer deadline day, cost United £30.75million in 2008 and was the Premier League's top scorer in 2010-11 but made just 12 league appearances last term.
Speaking at a press conference in Sofia, Berbatov told reporters: "I don't think I deserved such treatment at United - not playing in the last year. 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."
The beginning of the end appeared to come when the Bulgarian was left out of the matchday squad completely for the 2011 Champions League final against Barcelona, and he added: "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."
Berbatov found himself below Wayne Rooney, Javier Hernandez and Danny Welbeck in the Old Trafford pecking order last season and this summer's arrivals of Robin van Persie and Shinji Kagawa threatened his place further.
Berbatov felt he was the victim of a decision by Ferguson to play with a different style.
He said: "He tried to explain to me that the team will be using a more direct style, with more speed. 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."