Aston Villa's recent signing Carlos Cuellar could finally make his debut in Sunday's home Premier League clash with Liverpool at Villa Park.
The £7.8 million capture from Rangers has returned to full training after being side-lined with a calf injury.
The Spaniard is ineligible for Thursday night's UEFA Cup clash with Hafnarfjordur but is likely to be in contention to face Rafael Benitez's side.
Cuellar's availability against the Reds would be timely as Villa have conceded five goals in their opening two league games with Manchester City and Stoke.
O'Neill said: 'Carlos is doing well. It would have been great if he had been able to play a game before Sunday. I wish he had been eligible to play tonight.
'But he is making good progress. He has been training with us over the last two or three days and been doing really fine. He has done a lot of running as well.
'He is really keen to make his mark in the Premier League.'
Another summer capture in former Chelsea midfielder Steve Sidwell is also poised to resume training in the next couple of days after also being laid low by a calf problem.
O'Neill said: 'Steve is doing fine but wouldn't be as well advanced as Cuellar. He is doing pretty well although it feels as if I've been saying that for the last ten days.
'He is coming along nicely and I think he will probably be able to join in with us in training towards the end of the week.
'But we will not rush him back. What we don't want is a group of players who are only half fit going into the busy months of September and October.'