That will rule out former Liverpool boss Rafa Benitez, who is desperate to manage in the Premier League again, and ex-England chief Steve McClaren, out of work since his ill-fated spell in charge of Nottingham Forest ended in September.
O'Neill was soon installed as the odds-on bookies favourite to succeed Bruce and his DNA is stamped all over Sunderland.
The Ulsterman was brought up a Black Cats fan in his native Derry and, during managerial spells at Leicester, Celtic and Aston Villa, has never hidden his affection for the club. O'Neill has not worked since quitting Villa five days before the start of last season.
O'Neill has told close friends he sees Sunderland as a club with the potential to challenge the elite and has been impressed by the way Short has backed Bruce in the transfer market.