But the duo are centre-halves by trade – Cuellar making his name there at Rangers before his £8million to Villa Park and O’Shea (right) looking far more assured in the middle for the Black Cats after his £5m move from Manchester United 12 months ago.
With the pair now in their 30s too, O’Neill has confirmed that he wants to utilise them in their strongest positions.
O’Neill told the Echo: “Carlos’ best position is at centre-back.
“He has played at right-back for me, more times than either he or I would have wanted and did it really finely.
“But Carlos has a number of limitations in that full-back position.
“I probably see John O’Shea as a centre-half too. I think he’s more comfortable in that position.”
Cuellar’s arrival left Sunderland with six first-team centre-halves at O’Neill’s disposal, before the Black Cats boss allowed Michael Turner to join Norwich City last week.
Turner’s departure has boosted the chances of both Titus Bramble and Matt Kilgallon remaining at the Stadium of Light, with each having just 12 months remaining on their Sunderland contracts.
Kilgallon insists he was said to see Turner leave, but admits O’Neill’s capture of Cuellar has ramped up the competition for starting spots.
“We’re quite strong at centre-half,” said Kilgallon.
“Tina was a great player and I got on with him really well so I’m sad to see him go.
“I’ve played with him quite a few times. He’s a good defender and he’ll do really well at Norwich.
“Carlos has got the experience from his time at Villa, seems a great lad and it’s good to have him on board.”
Kilgallon is also confident that O’Neill can land the required signings in the next fortnight, with Cuellar the sole arrival on Wearside so far this summer.
The 28-year-old added: “I’m sure the gaffer knows what he’s doing. I’m sure there’ll be a few more in before the start of the season.
“I don’t think any teams have done a lot, QPR maybe, but that’s about it.”