"Kenny Dalglish once said it never works out that way because you always get injuries and suspensions.
"So we'll need to go back in and strengthen again which is my intention."
O'Neill expects new boy Reo-Coker to be a part of the Villa 'furniture' for years to come as he sets about moulding a side mostly in their early 20s.
"Power, energy and aggression are things that he will give us in abundance, and that's pretty necessary," said O'Neill.
"He's got youth on his side and I'm trying to get a young side together that's going to try to develop.
"I think they will do in time - it's only for old-timers like me that you want them to develop more quickly. But I think he'll be a driving force for us.
"He's packed a lot in in such a short space of time and that's all more power to him for being able to do it."