O'Neill had entered the month intending to significantly strengthen the smallest squad in the Barclays Premier League and maintain Villa's strong push for a European spot.
"We tried to also bring in Brad Guzan, an American goalkeeper with a lot of ability, only for the work permit application to be turned down.
"But January is a very difficult month, it is manic, a bit crazy. I made strong inquiries about several players I thought would strengthen the side but they were not available. It is as simple as that.
"In an ideal world, we would have liked to bring extra players in and, yes, I could have filled the squad with a number of people but I don't see the point of doing that just for the sake of it.
"We may have concerns over whether we get any injuries, but I have got great faith in the squad who have done brilliantly and we will go again now."