The Benin international was handed a lucrative contract extension two weeks ago but was virtually anonymous against Liverpool and his manager is demanding more.
O'Neill said: "With Stephane it's just not happening for him at the moment. Some things you can put down to lack of fitness, other things you can put down to not brilliant play, really.
"Some of the things that you expect of him, like being able to keep the ball, not giving it away early in the game, wouldn't have anything to do with fitness.
"So he just needs to get sharper in every aspect, sharper in fitness and sharper in the brain, because we know what he's capable of doing. But it's been a tough old time for him.
"I will try this week to leave out the lack of pre-season excuse, but he hasn't had much either. At some stage, even I could get fit after that! But I'll use it once more."