Sunderland skipper John O'Shea says they must not take their FA Cup replay with Fulham for granted.
The winners will meet Bradford City in the fifth round.
"People will look at Bradford City and how they were the big giant-killers from the last round against Chelsea, and it was obviously amazing for them to come from 2-0 down and win," captain O'Shea told his club's official website.
"They will be happy with a home draw but first and foremost we have a tough away game against Fulham, so hopefully we can progress but it is going to be difficult.
"The teams in the lower leagues have already shown how strong they can be, but as I said first off we have to take care of Fulham and we look forward to that."
