Ahead of Norwich's visit to the Stadium of Light, O'Neill's men are just six points above the relegation zone with nine encounters left to play.
With the Canaries three points and one place above the Black Cats, O'Neill has admitted that his team will have to "fight" if they are to collect a positive result.
"We need to start winning, really. I think next week is a big, big game for us," he told reporters. "We have difficult fixtures coming up, including Norwich. We have our work cut out. We have known that since the start of the season.
"It has been tough going throughout the season and we have to fight through these last nine games."
O'Neill had a brief spell in charge of Norwich back in 1995.