IT is the dilemma that managers describe as ‘a nice headache to have’, and Ange Postecoglou certainly won’t be complaining about having selection dilemmas on his hands ahead of Celtic’s Premiership opener against Aberdeen given he was scrambling to get any sort of team on the pitch for last season’s opening day defeat at Tynecastle.

So, while the ‘problem’ of deciding who will start for the champions at Celtic Park on Sunday is a relative one, it is a conundrum for Postecoglou nonetheless, and particularly in the hugely competitive midfield area, where six into three simply won’t go.

Last weekend, in Celtic’s final dress rehearsal for the season against Norwich City, Postecoglou started with Callum McGregor, Reo Hatate and Matt O’Riley in the centre of the park, hinting that would be his preferred trio for the Aberdeen game.

McGregor is nailed on of course as captain, while Hatate has been in brilliant form in pre-season, looking reenergised by the summer break. O’Riley too has hit stunning goals in the matches against Rapid Vienna and Banik Ostrava, so has a more than decent claim to a position in the team as well.

Matters are complicated though by the fact that David Turnbull is now back to full fitness, and indeed, came off the bench against Norwich to score with a trademark finish. Aaron Mooy, capped 52 times by Australia, is now in the mix too, and Postecoglou is known to be a huge fan of the 31-year-old, having previously worked with him when in charge of his national side.

Mooy, as evidenced in his late cameo against Norwich, is some way short of full match fitness, and so likely won’t come into the reckoning to start this weekend. But it may well be that his experience and combative qualities will be employed down the line when the Celtic midfield requires some added solidity, such as in the Champions League group stage.

Which all begs the question of where this leaves James McCarthy, the sixth midfielder vying for more first-team minutes. Were it not for the latest injury sustained by Yosuke Ideguchi, McCarthy may even be behind him in the pecking order, despite his own peripheral status in the squad since his arrival in January.

McCarthy was a player of undoubted quality, but he has yet to show that in a Celtic jersey since his arrival last summer after so many years at the top level in the English Premier League.

Perhaps it is age or his multiple injuries throughout his career that have caught up with him. Maybe he isn’t a good fit for Postecoglou’s system, with the prevailing notion being that the decision to hand him a lucrative four-year contract at the club at the age of 30 wasn’t necessarily the Celtic manager’s call.

Either way, it seems that barring an injury crisis, his best hope is to provide a supporting role from the bench, and perhaps get the odd game in the early rounds of the cup competitions. Moving on would seem to be in the best interests of the club, with the only question being whether the player wishes to wring as many minutes or as many pounds out of his remaining career as he can.

He would be well within his rights to choose either path, but one thing that is for sure is that he is well down the pecking order at the moment.

So, while in the long term Postecoglou may have a dilemma over whether Hatate or Mooy gets the nod, perhaps depending on the level of the opposition, the short-term call would seem to be whether he goes with O’Riley or Turnbull for the visit of the Dons.

Turnbull – or ‘The Bull’, as Postecoglou affectionally calls him – was one of Celtic’s key players in the first half of last season, carrying much of the creative burden from midfield prior to the arrival of the January reinforcements.

Indeed, the volume of football he played was a contributory factor in the hamstring injury he sustained in the League Cup Final win over Hibernian in December, that subsequently disrupted the second half of his campaign.

In his absence, the newly-arrived O’Riley stepped up in fine style, making a seamless transition from English League One level with MK Dons to make a huge impression on the Celtic support.

O’Riley scored four times in the second part of the season and looked a classy operator, while Turnbull returned before the Premiership trophy was lifted to chip in with his tenth goal for the campaign.

Either way, if both men can stay fit, perhaps Celtic won’t feel the absence of the departed Tom Rogic quite so keenly as they might have feared, and indeed, there may be times when Postecoglou feels emboldened enough to start with both men in the advanced midfield positions.

Whoever Aberdeen face on Sunday in the centre of the park, their midfield are sure then to be in for a long old afternoon. For my money, that will be McGregor, Hatate and O’Riley, and while there will be occasions when it may be ‘horses for courses’, it will be up to Mooy and Turnbull to fight their way into the starting XI on a regular basis.