Aaron Mooy has announced his decision to retire from football with immediate effect.

The Celtic midfielder leaves the game on the back of a treble-winning season.

And he called time on his international playing career too having represented his country 57-times including at the World Cup.

And it's being reported in his homeland that the reason for his shock retirement is down to an injury issue.

A report in The Sydney Morning Herald on Mooy's decision cites a "debilitating back injury" as the reason for his retirement.

It claims the back problems restricted Mooy's involvement with Celtic in the second half of the season and the issue was worsening, so he called time on his playing career.

Announcing his retirement, Mooy said: “While it feels really sad to be leaving the game, I just feel the time is right for me. I have been so fortunate to enjoy such a great career across the last 15 years, creating some fantastic memories.

"I am delighted to finish my career on such a high with Celtic and I would like to thank all the fans for the great support they gave me during the past year - I was delighted to be part of such a memorable season.

“I hope Celtic continue to dominate the game and I wish Brendan, the new manager great success with the great group of lads at the club.

“Playing for my country is something I have loved too and of course I will miss the international set up and so many great people who are involved there.

“I have been fortunate to win a number of caps for my country and this has been really important to me - of course I wish Australia nothing but success for the future and I am sure they can get better and better.

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“There are too many people to thank who have played such an important role in my career, so many managers, coaches, staff and fellow players. I have been very privileged to be part of some fantastic football environments, all created by really good people.

 “My family is everything to me and I would like to take this opportunity to thank them all for the absolute support I have received from them during my career.  I just want to thank them for being there for me in so many ways.

“Thank you once again to everyone who has supported me right across my career in this great game.”

Brendan Rodgers said of Mooy's decision to retire: “Clearly we are disappointed that Aaron will be retiring, however, it is something we absolutely respect. He has done so much in the game for a number of clubs and for his country and he deserves to make this decision on his own terms.

“I am delighted for Aaron that he has gone out on a real high after making such a telling contribution to Celtic last season and that, together with all his other achievements, should be a real source of pride to him.   

“Club football and the international game will miss him dearly, but on behalf of everyone at Celtic I send Aaron and his family our heartfelt best wishes for the future.”