Vidic had been linked with a move to Spanish giants Real Madrid in recent weeks, but United chief executive David Gill confirmed on Friday that the Serbian defender had agreed a new long-term deal with the club.
Ferguson said: “In the modern day game it is not easy renewing players contracts when they do well, particularly those from other countries.
“Over the last year or so there has been speculation about Nemanja time and time again, sometimes by the press, sometimes fuelled by other sources.
“But we never had a strong feeling he really wanted to leave. There is always concern if they do well they want better contracts.
“At the end of the day we have managed to achieve the task of getting him to agree a four-year contract.
“We are delighted, he is fantastic centre-half, a great competitor with a marvellous attitude to winning games. It strengthens our hand.”