Roy Keane is on the brink of a return to management after Republic of Ireland manager Martin O'Neil confirmed the former Manchester United captain has been in talks with Celtic.
The SPL champions are on the lookout for a new manager following Neil Lennon's decision to step down after four seasons in charge at Parkhead.
Celtic legend Henrik Larsson and former Swansea City manager Michael Laudrup have been closely linked with the role but Keane, who was appointed O'Neil's assistant manager of the Irish national team last November, has also been informally approached by the club.
"I had a call the other day from [Celtic's main shareholder] Dermot Desmond wanting to speak to Roy if it was at all possible, and I mentioned it to Roy, of course," said O'Neill, speaking ahead of his side's friendly with Italy on Saturday.
"I am sure he was wanting to have a chat anyway because a club like Celtic might not come around too often. It was just a really informal chat, I think, but if you are asking me would I be really disappointed? Of course, if Roy was to leave us.
"But I kind of felt that when I took him on in the first place, that over the course of the next 18 months to two years, that this thing was likely to happen. He was coming right back into high profile again. Perhaps I didn't expect it to happen so quickly. He has had a number of offers too from other football clubs as well, so he has obviously a lot to consider."
Former Republic of Ireland skipper Keane spent six months at Celtic following his departure from Old Trafford in 2005, only to call time on his playing career six months later due to injury.
Keane's managerial got off to an emphatic start when he got Sunderland promoted to the Premier League during his first season in charge in 2008. However after an acrimonious split with the Black Cats and a disappointing spell in charge of Ipswich Town, the former midfielder's reputation took heavy blows, leaving him in the wilderness until he was approached by the FAI last year.