YOU don't say no to a club like Celtic twice. Or so they used to say. While the great and good of world football once rolled up to give their sales pitch for a job like the Parkhead manager's position, now it is the club who must do most of the persuading. When you look down the list of runners and riders to replace Ronny Deila in the Celtic Park managers' office in the summer of 2016, what tends to unite them is some serious form for previously rebuffing the board.

After three league titles in three years, and more than occasional differences of opinion with the club hierarchy over recruitment, Neil Lennon decided enough was enough in May 2014. Soon afterwards Roy Keane, the man seemingly earmarked to take his place, was meeting majority shareholder Dermot Desmond over a cup of tea during an international week in Dublin but it didn't take long for his concerns to surface either.

"There would be one or two restrictions, about staff," Keane wrote in his autobiography, the Second Half. "They had already picked the man who would be my assistant and they were insisting on him. It didn’t scare me off but it did get me thinking. It wasn’t an ideal start. Were they doubting me already?"

Then, of course, there is David Moyes, favourite with the bookmakers, just as he was before the Keane connection arose in the summer of 2014. The messy tenure of the former Everton boss at Old Trafford had recently been brought to a peremptory end, but Moyes opted to wait it out before agreeing to a Spanish sojourn at Real Sociedad.

Also unsuccessful on that 2014 shortlist, not long before damaging details of his text conversation with Cardiff's former director of football Iain Moody torpedoed his chances of landing the Crystal Palace job, was Malky Mackay. Owen Coyle, now starring Stateside with Houston Dynamo in the MLS, preferred to stay at Bolton in 2010 when the question came his way. And whose sudden resignation caused that vacancy? Gordon Strachan.

So where do these 11th hour doubts come from when it comes to the lure of taking charge of one of the biggest clubs on the continent? And will the answers be any different this time, assuming the question marks remain the same?

The whopping TV deals on offer, south of the border, don't help, of course. They make the Scottish game seem pedestrian, provide a magnet for the continent's top playing talent and skew the wage market. While the board provided Ronny Deila with 21 players in two seasons, his own video analyst and his own physiotherapy team, how many of these new arrivals he personally drove or even sanctioned is unclear. Like all big clubs worth their salt, Celtic have a formidable recruitment apparatus to fall back on, but most managers worth their salt will seek guarantees which the board may not be able to give.

Being able to work in this system is one thing, dealing with the unrelenting demands from the fans is another. The predicament of Deila, shown the door for what appears likely to be two back-to-back title wins, is a case in point. "At least this is being done with a certain dignity, with the least amount of pain," said Alex Smith, of the Scottish managers and coaches association. "The club probably feel the need to have a more experienced person in charge of such a big club.

"The Celtic job is still a very, very attractive job but it is a very, very difficult job," said Smith. "In fact I would say that being manager at the Old Firm are the hardest jobs in British football. Walter [Smith] said to me after about seven years at Rangers that it 'isn't fun winning every week'.

"Now you also have a pool of people at the big clubs who are constantly searching, not only within the UK but the continent, looking for a special diamond capable of playing in Scotland and winning a big move to the Premier League in England too. Celtic have been operating that way and still being successful, still managing to win championships but not maintaining the same level of success they have previously had in Europe."

One reason why the answers could be different are that the precise circumstances of the protagonists have changed. Lennon would dearly love a second crack at the job after a wounding time, professionally and personally, in Bolton and is already au fait with how the club is run. Smith also feels both Moyes and Brendan Rodgers are worthy of consideration due to their work working within the apparatus of massive clubs like Manchester United and Liverpool, while the appointment of Roy Keane - a man who has "got the bravery, the guts and the gravitas for it" - could be similar to that of Graeme Souness at Ibrox in the 1980s.

While Moyes seeks a launching pad for his second run at the English game, Keane can't remain an international coach for ever. Martin, and Michael, O'Neill are also in the frame but it is at least worth pointing out an All-Ireland Euro 2016 final between the Republic and the North would be just three days before Celtic's first potential Champions League qualifier.