The sides meet in a friendly at Dublin's Aviva Stadium on Tuesday with most of O'Neill's first-choice XI either injured – in the case of skipper Seamus Coleman, seriously – or having been sent back to their respective clubs.
Robbie Brady, who was suspended for Friday's goalless World Cup qualifier against Wales during which Coleman suffered a double leg fracture, will wear the armband and lead out a side which will have a very different look about it.
Preston duo Andy Boyle and Daryl Horgan, Brentford defender John Egan, Derby counterpart Alex Pearce, Bristol City midfielder Callum O'Dowda, Leeds' Eunan O'Kane, Aberdeen's Jonny Hayes and Conor Hourihane of Aston Villa are among those who could benefit.
Manager O'Neill said: "You don't want to give out caps just because they are there, you want them to earn it. But for experience, you would want that.
"Some players who have just come into the squad - like the two lads at Preston - have acquitted themselves very well in training and they are basically just starting out in their international careers.
"Some players who have been around the squad but haven't played regularly may well play as well, and whatever length of time they have on the pitch tomorrow evening, it's a chance to try to impress, and that is what they will try to do.
"There are a couple of lads who have gone home - Jonathan Walters and Glenn Whelan - so they won't play.
"In all honesty and in fairness to clubs, some of the lads who played on Friday night who are still with us certainly won't start in the game and might not participate at all."
The game will bring together two sides who impressed at last summer's Euro 2016 finals, with Iceland going a stage further than Ireland by reaching the quarter-finals thanks to a victory over England.
They are currently ranked 23rd in the FIFA rankings, one place higher than the Republic, and like O'Neill's men sit second in their World Cup qualifying group, in their case after a narrow victory in Kosovo on Friday.
O'Neill said: "Iceland were brilliant at the Euros, they won on Friday night and they'll present us with a few problems.
"But I'm hoping that the lads who will start in the game and who will come on will actually go and basically press a claim for future international matches."
