It also took some of the shine off a 35-yard wonder strike by Sammy Clingan whose goal was worthy of any stage.
After Saturday's clash at Deepdale, a delighted Irvine said : "It was vitally important for us to win, we didn't want everyone linking Sean's departure with us not being able to get results.
"I said today that we needed to be braver to take the ball, be prepared to take responsibility rather than hope somebody else might take it, might turn things around.
"The lads showed great character to dig deep. Goals change games drastically.
"Today wasn't a day for blasting anybody. I felt we were a bit nervous at the start of the game, not very driven on the ball and giving it away very cheaply.
"Last year we probably didn't get enough goals from our front players. The second goal of ours was fantastic. It was a counterattack you would be drooling about if you saw Arsenal or Man United doing it."
Irvine had particular words of praise for two-goal hero Chris Brown who has now bagged six in all competitions.
He said: "Last season Chris had a back injury and it never really cleared up. He is a really important player for us."
Sky Blues boss Chris Coleman was left feeling that defensive lapses had cost them their trip to Deepdale.
He said: "Overall in the 90 minutes we had the better chances. We should have done better with some of our chances.
"We are better than that defensively. I think we were tired from Tuesday, we were affected by that, unfortunately.
"We are at our worst when we have had a couple of decent games. We had lapses in the game today and were not hard enough mentally.
"We gifted Preston with two goals, gave them away. They are a good enough team, they don't need to be given any presents.
"That's why we are not top six or 10 and not in the Premier League. You have to do it week in week out.
"There were positives to take away though. Sammy's goal was an absolute stunner. I think we deserved it as well.
"Right after that we had a couple of chances where we should have scored but didn't. That second one is so important.
"It is no good having to score three or four goals in games to have to try and get points.
"We have to get back to being mean."
Northern Irish midfielder Clingan will probably never score a finer goal than his free kick which set Deepdale alight after 19 minutes. His 35-yard strike hit the roof of the inside netting as it thundered in.
Keeper Andrew Lonergan pulled off four great saves for Preston - three of them from Leon Best and one from Clinton Morrison - but he could do nothing to prevent Morrison knocking in a late consolation goal after Eddie Nolan tried to head back.
Preston looked below par before their amazing comeback started four minutes after the break.
Chris Sedgwick's cross was hooked in by Chris Brown from several yards out, Neil Mellor grabbed the second from Jones's cross about five minutes later and Brown's second goal arrived at close range after keeper Keiren Westwood parried the ball.