O'Neill is relatively relaxed about the free transfer's impact - or lack of it - but admits the player has found it hard to take.
He said: "I think Louis has been a bit disappointed. When he first came, I told him I wasn't expecting miracles of him. He'd done no pre-season training but I was hoping, over a period of time, he would make an impact.
"There was talk about us being interested in Bolton Wanderers' Kevin Davies last season, and I thought he might have been able to come in and do a half-decent job himself, but also help improve the young centre-forwards like Connor Wickham.
"It's been really tough for Louis. In training, in the small-sided games, he's been absolutely terrific.
"He's a bit disappointed he hasn't been able to take that on to the field."