The England striker was recently dropped for a home match against Blackburn Rovers by Ferguson after performing poorly in training following a Christmas night out.
When asked whether he was angry with the decision to fine him a week's wages, Rooney told La Republica: "Yes, but for reasons that I can't make public.
"I accepted it. But I was tense when I got back on the pitch and I believe it showed.
"The life in a dressing room, between players, between us and the coach, between us and loads of people, it's continuous confrontation and at times it's harsh."
Rooney was linked with a move away from Old Trafford but the 26-year-old and his club have both strongly denied the reports.