The 31-year-old fell out of favour under old boss Gerard Houllier. Houllier was replaced by Alex McLeish as Villa boss in June.
Dunne said: “I probably would have left if Houllier had stayed.
“But once there was a new manager coming in, I knew I had a chance to stay.
“I spoke with him when he took over and he said he heard of stuff that happened at Villa last year.
“He said if we recaptured our form, he wanted myself and James to be his main centre-backs. That gave us confidence right away.”
