Chris Cohen's goal for the home side settled the game but O'Neil is adamant the only difference between the two sides is their levels of concentration.
It was Forest who created the first chance, with Chris Cohen's cross almost finding Rob Earnshaw in the box only for a defender to nick the chance away from him.
Burly journeyman Dele Adebola proved to be a nuisance for defenders Danny Gabbidon and Herita Ilunga, while man-of-the-moment Lewis McGugan and ChrisCohen were beginning to combine well for the visitors on the right.