"I found it hard to settle in Manchester and at United," he admitted.
"When I moved to Moscow it was easy because there were five Serbs in the Spartak team, but at United there was nobody. In Manchester people didn't know much about me.
"I know everyone was asking whether I was good enough to play for United. I felt as if I had to show something always, in training and in matches.
"I'd had some injuries, too, and the Premier League is more physical than I had experienced before. After a couple of months I said to myself: 'This is not the right club for me'."
Sir Alex Ferguson begged to differ, though.
"I was very down for a while but the manager kept telling me he believed in me and that I'd come good and be a big player," said Vidic.
"That really gave me confidence, and when my partnership with Rio Ferdinand started to work, I began to show what I can do.
"Rio (Ferdinand) and I, although different people, are good communicators on and off the field. We have a good relationship and it's because Rio has always been very open with me. In a game we hardly need to talk. I know exactly what he's going to do next, and where he's going to be, and Rio knows the same about me."