Since the Ulsterman's arrival at the Black Cats in late November, the Wearside club have been propelled to safety and now sit comfortably in mid-table.
But, with on-loan Nicklas Bendtner due to return to Arsenal and UAE-based Asamoah Gyan unlikely to play for the club again, a quality forward is what O’Neill wants this coming transfer window.
He told reporters: "We don't have anybody in double figures at this moment scoring goals.
"At the end of the season, if you are going to have some sort of success, you are going to have to have that.
"You are going to have to have at least two players in double figures and possibly three, and one of those scoring a quite substantial number over 10, for a start.
"We have disguised the fact over the weeks by being able to share them around, but when they are not coming from other areas, then of course you start looking at centre-forwards and scoring goals.
"You have got to be in positions to score goals. We need to be able to do that, we need to do it more often and we need to be able to score goals inside the six-yard box."
O'Neill praised Llorente after his efforts in Bilbao's Europa League win on Thursday night but admitted such a move was a little unrealistic.
He added: "Have a look at Athletic Bilbao's game last night - the centre forward there was prepared to come out and play. He's a brilliant centre-forward."
The Northern Irishman added with a smile: "Is he available?"
The manager has yet to sit down and talk about potential signings with club owner Ellis Short and O’Neill acknowledged any financial decisions would need his backing.
"That will be pretty important, to see what his views are for the football club, and to put my own views across as well," he continued.
"Ellis wants to do well by the football club and I think it will be interesting to see how things develop."
Sunderland sit 11th in the Premier League - two points away from eighth and also 14th - and the former Aston Villa boss is targeting a top-10 finish for the Black Cats.
"A few months ago, I certainly thought we wouldn't have the number of points on the board that we do have now," O’Neill said.
"So from our own viewpoint, it is actually a relief not to be involved down there, a genuine relief.
"It would be great if we could finish in the top 10. It wasn't my target in December, but after we had hauled ourselves out of the relegation zone, then of course you start to set other targets.
"It would be nice. That is an aim."