Richardson played alongside the Irishman at Man Utd and was later managed by him at Sunderland.
"That season when I signed for Sunderland I think I only played 10 games because I had a hairline fracture in the L5 vertebrae in my spine," said Richardson to Villa's website.
"Throughout that season I was very upset, I put on a lot of weight and I got bigger.
"But just before the end of that season, Roy took me into his office and we had a massive conversation.
"He inspired me to go away in the summer and come back in better shape than I had ever been in.
"I went and played very well in the next season.
"He gave me some good words of encouragement to go and do that over the summer and I appreciate that."
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