Aberdeen captain Paul Hartley has quit the game at the age of 34.
The Dons have cancelled the former Scotland international's contract, which had a year left to run.
Hartley last played in Aberdeen's Scottish Cup win over St Mirren in March but suffered a medial ligament injury in a collision.
After a career which began at Hamilton, he now plans to work as a coach for which he has been working towards the necessary badges at Largs.
"It's something that has been playing on my mind for the last two or three months," said Hartley.
"I felt that I couldn't perform at the level I wanted to and meet the standards that I have set over my career."
A statement on the Aberdeen website said: "Everyone at Pittodrie would like to thank Paul for his contribution over the past season, which has been excellent, and we wish him all the very best for the future."
After the Cup win over the Buddies, Dons manager Craig Brown had hoped to be able to call on Hartley's services for the semi-final with Celtic, but the player broke down and this is what confirmed his decision to retire.
Hartley picked up the last of his 25 caps in Craig Levein's first international - a friendly win over the Czech Republic, though he would later be selected for the squad that faced Lithuania and Lichtenstein at the start of the current Euro 2012 qualifying campaign.
After Hamilton he had spells at Raith Rovers, Millwall, Hibernian and St Johnstone.
But it was his exploits at Hearts which brought him into the limelight as he helped the club win the Scottish Cup and split the Old Firm in 2006.
That earned him a two-year spell at Celtic where he won two league titles, a Scottish Cup and a League Cup - whilst also scoring the goal against Spartak Moscow which confirmed the Parkhead side's participation in the 2007 Champions League.
He joined the Dons after a year with Bristol City and was instantly made club captain by Mark McGhee. Remarkably, he scored a hat-trick of penalties on his debut against Hamilton.
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