O'Neill admits he rejected enquiries for Campbell during the summer.
"Fraizer has a battle on his hands - as have the players I have brought in," O'Neill said.
"I think everyone wants to be a part of it and I think there is a just a lift with the new players coming in to the club. The position are there for battle and we will see.
"When I came in here Fraizer had been injured for a long time. He came back and not too may come back from those injuries, and the good thing is that he is injury-free.
"He came in a flurry last season which was really great but like most of us, he dropped a little bit after the Everton game. We have tried to regain it in pre-season.
"There was a bit of tentative interest in Fraizer, as there was a number of my boys but I would not want to leave myself short with the number of strikers we have."