The Bulgarian joined the Red Devils for £30 million in 2008 after impressing at Tottenham and lifted two Premier League titles during his time at Old Trafford.
However, he began to fall out of favour toward the end of his time with the club, a situation underlined by his failure to make the squad for the 2011 Champions League final against Barcelona.
And, following his deadline day move to Fulham, the Bulgarian has underlined his unhappiness during that period.
|8.50||Fulham are 8.50 with Bet365 to beat WBA 2-1
"I don't think I deserved such treatment at United – not playing in the last year," he 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."
The 2010-11 Premier League top scorer also claimed that a change of style from Ferguson led to his prolonged spell on the sidelines.
"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."
Berbatov had been rumoured to be close to joining Serie A giants Juventus and Fiorentina before jumping at the opportunity to work with Martin Jol again following the pair's successful spell at Spurs.
Fiorentina later slammed the 31-year-old for his indecision on deadline day, something which the Bulgarian insists is not his fault.
"I've never personally told them, 'Yes, I'll play for you'," he continued. "It's not my problem that someone is disappointed. After all, I choose where to play and be happy.
Berbatov concluded: "It's stressful. One club called, then another, and a third, and then another. A man can go crazy at one point. I'm a human being and it's normal for me to hesitate."