Celtic fans have plenty of questions when this season comes to an end. When the Celtic players emerge from the tunnel to take on Rangers on Sunday at Celtic Park, every single person associated with the club will roar as one. That unity of purpose will persist until Celtic have won the title or lost it for only the second time in 15 years.

But while Martin O'Neill's steadying presence has kept Celtic in the hunt in the title race and Scottish Cup, questions about next season simmer in the background. Nobody appears closer to knowing who the club's new manager will be, how their football department will look, and whether it will be the same faces in the boardroom amid fan unrest. A period of unprecedented domestic success is under serious threat, and how Celtic respond is a source of rancour, debate, and fascination for many, not least the supporters.

All the latest Celtic news, views & analysis Three becomes two in Premiership title race - fan views. O'Neill says Hearts can be regular title contenders. Over his two spells in charge this season, 74-year-old O'Neill has averaged more Premiership points per game than any of his peers. He has been more successful than Celtic could have hoped for when they brought him out of retirement after Brendan Rodgers' acrimonious departure, and again following Wilfried Nancy's ill-fated eight-game spell.

There is at least an arguable case that had he been in charge since Rodgers left, Celtic would be strong favourites to win the league by now. On that basis, has O'Neill done enough to return as manager next season? Is his future contingent on winning the Premiership? Should Celtic look to the future? Does O'Neill want to keep managing in such a harsh environment at 74? Right now these are unanswered questions, at least outside the walls of Celtic Park.

"I feel a sense of renaissance, coming back and working with young people, it's really, really terrific," O'Neill told talkSPORT on Tuesday when asked about the future. "We'll have to see how we stand at the end of the season, and that's nearly upon us now."

While grateful to O'Neill, who was already a legendary figure, some Celtic supporters feel a fresh face in the dugout is needed. Paul John Dykes, from A Celtic State of Mind podcast, believes O'Neill "should go and chill out and just enjoy retirement" at the end of the season.

"Martin O'Neill has been dreadfully let down by the Celtic board," Dykes told the BBC's Scottish Football Podcast. "There's no way he came to Celtic in January, one week into a January transfer window, on the promise of four loanees and an out-of-contract player to win the double. No chance."

"So regardless of what happens, Martin O'Neill's legacy is intact." The only other names who have been talked about regularly as potential successors are Robbie Keane, at Ferencvaros, and Jens Berthel Askou of Motherwell. Keane, 45, declined the opportunity to talk about his future beyond the end of the season in interviews this week. The former Republic of Ireland international is aiming to finish the campaign with a second Hungarian league title, adding to the league he won in Israel with Maccabi Tel Aviv. Keane's knowledge of Celtic, experience of winning and European football make him an attractive fit.

Meanwhile, Askou's work at Motherwell has drawn admirers across Scotland. In his first season in the country he has taken a side who finished in the bottom half in the past two seasons to the cusp of European football. All while playing an attacking, adaptable, and intense style of football with players boasting a sliding scale of abilities.

"It's a style of football in Scotland I've not seen, probably outside of Ange Postecoglou's Celtic," Motherwell midfielder Andy Halliday said on BBC Radio Scotland's Sportsound regarding Askou's impact at Fir Park.

"When you take into account you've got Paul McGinn at 35, playing the best football of his career, Stephen O'Donnell at 34 playing the best football of his career. How many sellable assets has Askou put in Motherwell's team? Clubs will be interested in Tawanada Maswanhise, Elliot Watt, Lukas Fadinger, Emmanuel Longelo and all these players. He's transformed the club financially as well."

Icons of Football: Henrik Larsson. Rancour and protests in the stands have been as much a fixture of Celtic's season as the action on the pitch. There have been banners galore, tennis-ball protests, and chants aimed at those on the club's board. Chief executive Michael Nicholson, major shareholder Dermot Desmond and former chairman Peter Lawwell have shouldered the brunt of the criticism.

Lawwell resigned in December because he said "abuse and threats" had become "intolerable". The Green Brigade ultras group, who are some of the most vocal critics of the club, were banned for anti-social and threatening behaviour before coming to an agreement last month to return. Some Celtic fans - and plenty outside the club - feel the criticism levelled at those in charge is unfair given their domination of Scottish football for 20 years.

Celtic fans have called for the club's board to be removed throughout the season. But a significant proportion believe the club has become too comfortable with domestic dominance, slow to embrace changes in football recruitment, and presiding over a period of poor European results. A series of underwhelming transfer windows and a failure to qualify for this season's Champions League exacerbated those frustrations.

Interim chairman Brian Wilson announced this week the club will be investing in a "supporter engagement department" as they seek to improve relations. Appointing a sporting director with a good track record in a modern recruitment structure would also hint at a possible change in approach.

But will that be enough for fans who think change at the very top is the only solution? "I was listening to the chairman last week and it was the usual waffle that we get from the Celtic boardroom," John Dykes said on the Scottish Football Podcast. "'We've made mistakes, we're aware of the mistakes, we'll put them right'. You won't, because it's the same people, it's the same heads, same culture."

Not every Celtic supporter would agree with that assessment. But what is clear is that - whether Celtic win a 14th title in 15 seasons or not - all of these major questions will need answers. From the pitch to the boardroom, a big summer awaits Celtic.

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