The news comes as no surprise, as the Bulgarian is battling the acute leukemia he was diagnosed with in March 2012, but it remains no small blow to take.
He enjoyed an illustrious career, starting at CSKA Sofia, moving to Celtic where he collected eight winners' medals, then onto Aston Villa to follow manager Martin O'Neill.
Throughout his time in the United Kingdom his game changed a lot: He went from an attacking, incisive No. 10 with a long shot that worried goalkeepers, to an interception machine from defensive midfield, stopping attacks and cutting out passes all over the pitch.
He went from the quiet one who couldn't assert himself in a particular position at Villa Park to the dominant, inspiring leader he is today.
But while on-the-pitch changes have been dramatic, the kind-hearted man has remained. His retirement statement was more a "thank you" statement, taking the chance to give thanks to all his influences:
I wish to thank the fans of Aston Villa and the Villa chairman, Randy Lerner, chief executive Paul Faulkner and manager Paul Lambert, also the fans of Celtic, the Bulgarian fans and fans of football all over the world who have helped me through the past year with their incredible displays of support and with their personal, moving messages.
I would also like to thank all of the managers I have worked under and all of the team-mates I have played alongside.
He has also embodied the fighting spirit of a club finally taking steps in the right direction and remained a professional presence throughout his duration at Villa.
Under Gerard Houllier things weren't comfortable, and many players—the likes of James Collins and Richard Dunne—struck out, but Stiliyan remained conservative.
Alex McLeish came along and players struck out again, but the Scot valued Stan highly, and he responded to that praise, remaining professional and focused on the relegation battle.
The Villa side of 2012-13 have been fighting all season to avoid relegation and finally look to have achieved that; Stiliyan Petrov's private battle with cancer has seen a 19th-minute applause occur in every single game this season, and with it a feeling of togetherness, of collective fight.
The fans and Petrov were in it together; the team and Petrov were united. He's going to be a big miss to the game, and he's respected all over the world.
Villa fans will be desperate for him to complete his recovery, return to health and then involve himself further with the club: A coaching role has been suggested by Paul Lambert, who will aid his old friend in any way possible.
Thanks for the wonderful years of service Stiliyan, we here at B/R wish you the very, very best.