The two clubs meet in the Capital One Cup tonight.
Ferguson told Posh Player: "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."