"I know people sometimes think I don't care. Trust me. I do," he said. "I get frustrated and if I don't play well I am very disappointed.
"People should not just look at my face and make an assessment about me, depending on what it shows."
Ferguson pursued Berbatov for well over 12 months, believing the former Spurs star could add an ingredient missing from his team by being able to unlock the tightest of defences in the most difficult of games.
A tally of 14 goals and an equal number of assists suggests Berbatov has added a bit extra.
Yet as the season has reached its dramatic conclusion, he has been gently eased out of the United starting line-up.
Indeed, it is now expected Berbatov will be on the bench in Rome on Wednesday night as United attempt to join Ajax and Bayern Munich among the list of clubs that have won the European Cup on four occasions.
"I know what I have done. And I know I can do a lot more," he said.
"I can improve because I didn't produce 100% in some of the games I have played since I came to the club."