The Black Cats sit 16th on the Premier League table and O'Neill is well aware that he needs to strengthen his playing group in order to improve that standing.
"I think that we would have to seriously look at strengthening the side in January," he said in the wake of the 3-1 loss to Manchester United on Saturday.
"We don't have any great numerical strength, and we've got a few injuries. You're going to get that, and we have to try and cope with it. It's inevitable when you don't have strength in depth."