The Black Cats' victory against relegation rivals Wigan last weekend lifted them to 14th in the table.
"Obviously, Derby are struggling but I won't write anybody off until they are mathematically relegated.
"You still have a chance until the mathematics tell you otherwise."
Sunderland are four points and four places above the drop zone but are still very much involved in the struggle for survival, along with the bottom three and Birmingham, Wigan and Bolton.
"Some people were perhaps surprised that it came against Villa, but I wasn't particularly surprised - you can get good results against anyone.
"We just have to focus on ourselves and get points on the board. If we do that, then whatever the other teams do is irrelevant."