The Serbian defender had to be persuaded to stay by United boss Sir Alex Ferguson, as he struggled to settle.
“I found it hard to settle and I know everyone was asking whether I was good enough to play for United,” said Vidic in the Daily Star.
“I’d had some injuries too and the Premier League is more physical than I’d experienced before.
“After a couple of months I said to myself, ‘This is not the right club for me’.
“I was very down, but the manager kept telling me he believed in me and that I’d come good and be a big player. That really gave me confidence.”
He added: “Right now it is like a track-and-field race. The two leaders, Liverpool and Chelsea, are at the front of the race with one lap to go.
“We are sitting just behind them on their shoulders, looking nice and comfortable and ready to choose the moment to strike for the finishing line.
“The next two months will be very important and I’m sure the race to be champions will be tight this year.
“But I think we are in a very good position right now and I am happy where we are.”
