While Villa's defence has a reputation as one of the meanest in the top flight, their lack of goals is something O'Neill is keen to improve upon. They have scored fewer than any of the other sides in the top eight - managing just 46 in 33 Premier League games.
O'Neill thinks their play should produce more goals and he said: "I wouldn't disagree that the lack of goals from the chances we create and the flowing football that we play has been a problem.
"The crowd is up whenever our attackers pick up the ball expecting a goal.
"From all the play we have and all the possession we have I'm not sure we score the requisite number of goals that our play should command."
While O'Neill wants to see more goals, he has been highly impressed with the way that his rebuilt defence has performed this season at the opposite end of the pitch.
O'Neill signed Richard Dunne, James Collins and Stephen Warnock last summer and, excluding the aberration at Chelsea when they conceded seven goals, the Villa back line has proved to be a formidable barrier this season.
"At £5million each Dunne and Collins have been phenomenal value," added O'Neill.
"Sometimes I wonder where we would have been if those two and Stephen Warnock had not arrived in relatively quick succession.
"They have formed the backbone of our defence. Carlos Cuellar has done magnificently as well, often playing out of position.
"So I've been absolutely delighted with the team, which is
improving, and the support from the fans has been enormous."
While Villa will be facing a Portsmouth side who are already relegated, O'Neill is not taking anything for granted as the Pompey players are vying to stake a claim for a place in their FA Cup final line-up.
O'Neill is full of praise for the way that Pompey manager Avram Grant has guided the team to the FA Cup final against a backdrop of the club going into administration and being relegated.
He added: "Avram Grant came into the club in difficult circumstances.
"For the want of a better word he has 'divorced' the situation and took what is happening politically away from the players.
"I think in many aspects the pressure went off them and they could concentrate very heavily on the FA Cup and I fully expect the Portsmouth players to be in a relaxed frame of mind when we play them."