The winners will face City if they can overcome Manchester United in their semi-final showdown.
But central defender Dunne, who spent nine years with the Blues, is adamant all his focus is on helping Villa to win a trophy and claim the first silverware of his own career. He said: "I really enjoyed my time at City. It was nine years of my career so it doesn't just go away.
"But the aim is to win a trophy for Aston Villa. I didn't manage to do it when I was at City.
"The opportunity is here, and if it is Manchester City in the final, then we have to do our best to overcome them.
"But I haven't thought about the prospect of playing them.
"And if you look at Manchester City and Manchester United, it is nearly impossible to call these days (who will win). For us, it is just about Aston Villa.
"The aim is to get to the final and, come the end of February, to be picking up the trophy. That is the main thing for me, whoever we play."
Dunne expects City to be active in the transfer market during January at the start of the Roberto Mancinin era.
He said: "When I was there, there was not just one player but four or five linked to the club every day.
"But that is the way Manchester City is. They are a big club with a lot of money to spend and obviously the owner's dream is to win the Premier League so a lot of players want to go there."
Villa were due to visit Blackburn on Tuesday but the bad weather led to the game being postponed.
After the January 14 Blackburn clash they face West Ham (January 17), the return leg with Rovers (January 20), the home FA Cup tie with Brighton (January 23), a home league game with Arsenal (January 27) and a trip to Fulham (January 30).