The Northern Irishman labelled Villa as a 'strong side' and seemingly expressed his surprise at them being so low down in the table given their performance at the City Ground.
The home team took an early lead through Jack Colback's lucky cross/shot before John McGinn levelled the scores with a finish at the near post. The Scot then doubled his side's lead with a brilliant low drive from 25 yards out before defender Kortney Hause made sure of the points in the second half.
After the match, speaking to Sky Sports News (13/03/2019 at 10:25 pm), O'Neill shared his thoughts on the encounter and the goals his team conceded.
"Disappointed, obviously," O'Neill told Sky Sports News. "Getting beat here against a very good Villa side. Off to a great, great start. We conceded from our viewpoint a poor-ish goal to equalise. Villa got a bit of momentum going and got 2-1 in front.
"I thought we had quite a lot of possession in the second half and the third goal was obviously a bitter blow for us at the time and we never really recovered after that. Villa are a strong side. I suppose you have to wonder why they're in that position in the first place."
Last month, after Villa's home defeat to rivals West Brom, many supporters were in agreement that the club's hopes of finishing in the top-six were over.
The Midlands outfit, prior to a couple of weeks ago, had only recorded two wins since the end of December and were struggling without their star man Jack Grealish in the side.
But ever since he returned from injury against Derby County, Villa have gone from strength to strength, they dismantled the Rams, beat Birmingham City over the weekend and now picked up valuable points away at Forest.
As a result of that change in form, Dean Smith's side are now two points outside of the top-six as three points at home to Middlesbrough at the weekend will see them move into the play-off places.