Cole left City last summer and is now playing for Bradford City.
"Vieira did a lot of good for me. At the same time, we clashed a lot," he admits to the Daily Mail. "It was our personalities. He doesn't like people who answer back and say what they believe. I will be open and say, 'I don't agree with you'.
"But I think our differences probably helped me do well, I wanted to show him."