United striker Wayne Rooney went from wanting to leave Old Trafford to signing a new deal worth at least £160,000-a-week this week.
“The players are no problem. Some agents are difficult,” Ferguson said.
“It is always tough at United. There are always issues to deal with. When your top players come towards the end of their contracts you have to do something to get them a new one.
“They are all the same. You have to deal with agents of this world today, which is difficult.”