The Senegal international defender played his first competitive match since his loan move from Saudi Arabian side Al-Hilal when he turned out for the Black Cats' Under-21s side last week, and is gradually building up match fitness.
However, O'Neill is keen to look at the 29-year-old, who was an unused substitute for Saturday's 2-2 draw with Fulham, in the heat of Barclays Premier League battle, although is reluctant to do so while his side still needs to amass points to climb to safety.
O'Neill said: "He's improving in terms of fitness, and that is good news for us. If we had a few more points on the board, I think then you could risk throwing him into a game.
"At some stage or another, he will play because we want to find out exactly what he is capable of doing.
"He will just have to bide his time, but I would like him to be as fit as he possibly could be when he gets that opportunity."