In-form Posh will be looking to increase the misery on Wearside on Tuesday night but Ferguson will instead now be going head-to-head in the technical area with Black Cats caretaker boss Kevin Ball.
Sunderland's sole victory this season has come in this competition after they staged a late turnaround to see off MK Dons 4-2 in the last round.
And the managerless outfit are guaranteed another tough task against a Sky Bet League One side who have won eight of their 10 games to date, including respective 5-1 and 6-0 victories over Colchester and Reading in the Capital One Cup.
Speaking about Di Canio's departure, boss Ferguson told Posh Player on the club's official website: "It doesn't affect me, it may affect Sunderland.
"Generally, when there's a change of manager in the short-term normally there is a reaction, for whatever reason. Whether it's going to make a difference I don't know, you'll find out on Tuesday night.
"I was quite surprised, I have to say, he's only been there six months so I think most people would probably, even though the results haven't been going well, I thought he'd be there longer than that."
Ferguson added: "We've got to go there and make sure we put on a good performance, the aim is to go and try to get through, otherwise there's no point turning up, really.
"We know it's going to be a tough game, they've got some really, really good players but we know on our night we can give teams a game and we're going to have to perform right at the top of our game to get through the tie."
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