"I have seen some comments that this must have been set up before I left Pompey but nothing could be further from the truth," he told the club's official website.
"I never dreamed I would be offered this job. I thought it could never happen because I had been at Pompey.
"I was looking forward to my break but then over the last 48 hours things all happened very suddenly.
"I walked away from Pompey without a penny and left a contract worth an awful lot of money.
"Those reasons are well documented. The chairman felt there was a need for a director of football and that was not a road I wanted to go down.
"I never had any idea anything like this would come up. In fact I was not even sure I wanted to go back into football.
"I had one or two calls but they did not interest me. I planned to take six months or a year and then see how I felt.
"But this was a challenge I could not turn down and if it had not been this club, then I don't know if I would have gone back into football.
"It is a terrific club and I always said that when I was manager of Pompey."