"I found it hard to settle and I know everyone was asking whether I was good enough to play for United," he told 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."