Cattermole played the last quarter of an hour of Tuesday's dismal FA Cup third-round replay defeat to Bolton at the Stadium of Light after sitting out since November with a knee injury.
But with doubts over striker Steven Fletcher for Saturday's vital Barclays Premier League trip to Wigan due to a virus, O'Neill has warned his team must learn to cope with the absence of key men.
O'Neill said: "Lee has been missing for seven or eight weeks and I am hoping he can stay fit for us between now and the end of the season. I did think about starting with him, but I was not sure how he would cope physically.
"Steven came in to do a little bit of work (yesterday) and that was when he was feeling ill and we sent him home. I am just hoping he will recover in time for the weekend.
"Fletcher (would be) a big miss for us, but we should be able to cope. The whole idea of trying to get a team and a squad together is that there are going to be good players missing.
"We have got to galvanise ourselves and show more consistency. We have got to be able to go two, three, four, five games together in which we put everything into the game. I think we should demand this."