Irvine said: "I was probably in as safe a job as you can get. I could have rode along on the back of David Moyes for many years.
"I would have been very happy doing that because Everton was a fantastic club and I had a wonderful boss.
"But I was offered the Preston opportunity and I felt that if I hadn't taken it, I would have shown a lack of ambition. Being a manager was the only thing in football I had never done."