O'Neill is racing against time to strengthen his small squad before the transfer window closes next week.
He will not comment on specific players but has admitted boosting his defensive options is a priority, with a new centre-half at the top of his wanted list.
Villa lost the commanding presence of captain Martin Laursen when he was forced to retire due to a knee injury in the closing stages of last season, while they also sold Zat Knight to Bolton for £4million earlier this summer.
O'Neill said: "I cannot comment on any individual. But we are still looking to bolster the squad.
"It goes without saying that defensively we are still looking for a Martin Laursen-type player and it is not easy in this day and age.
"I hope that we will be able to get in a new player before the deadline but until you get the players actually signed it would be difficult to comment.
"But we know that we have about a week to get the squad together."
O'Neill has admitted setting up deals has proved to be tough this summer, and he added: "I think the proof of how difficult it might be is in the fact that a the number of clubs have not done a great deal of business.
"I am talking about Premier League clubs. That might tell you something and of course the market gets a bit disjointed as well and everything has a follow-on effect.
"All of those things are taking place at this moment but I am hoping we will be able to add some players to our squad because it will be important to us in the coming months."
O'Neill currently only has two senior central defenders to call on in the shape of Carlos Cuellar and Curtis Davies, while his options at full-back are also restricted with Luke Young having recently been on compassionate leave and Wilfred Bouma continuing the long haul back from a dislocated ankle.
While O'Neill battles to add to the summer additions of Stewart Downing, Fabian Delph and Habib Beye, he has acknowledged Monday night's stunning 3-1 win against Liverpool at Anfield has given the whole club a boost.
Defeat against Wigan on the opening day of the season got Villa's campaign off to the worst possible start and was swiftly followed by a 1-0 loss in the first leg of their Europa League tie against Rapid Vienna.
O'Neill added: "Something I hadn't looked at when fixtures came out was that before we kicked off at Liverpool for our second game a lot of teams had played three matches.
"It is points on the board which matters and we now have three points, which is something to build on.
"It was kind of catch-up after only nine days of the season so it's very pleasing to have won at Anfield and there is plenty to look at for this week."
Villa host Vienna in the second leg of their Europa League clash on Thursday night.
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