At the time, Campbell was competing with some top quality players at Old Trafford so felt he needed to leave to give himself the best possible chance of succeeding at the highest level.
"It was difficult to leave United. I'd been there since I was 10," Campbell told the Daily Star Sunday.
"But I wanted to be playing. I have no regrets, though, because you have to be realistic.
"Then they brought in Carlos Tevez. I had to be worth £25million to be playing in that team!
"I had a great time there. I didn't play many games but it was nice to be part of the club."
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