Shaquille O'Neal says he is retiring from the NBA after a professional career spanning nearly two decades. O'Neal, 39, made the announcement via a video he posted on social networking site Twitter. "We did it. Nineteen years baby. I want to thank you very much, that's why I'm telling you first, I'm about to retire," O'Neal said in the message. A spokesman for the Boston Celtics - O'Neal's current team - says the player has not notified them of his plans. O'Neal has been affected by injuries in the latter stages of his career during his time with Phoenix Suns, Cleveland Cavaliers and Boston. He has played just 37 games this year, which is the first of a two-year deal at the 7ft 1in player's minimum salary. He has made just three appearances since 1 February. He recently told an ESPN reporter working on a biography of him that he had considered carrying on playing despite a nagging right Achilles problem - but did not want to disappoint Celtics fans. "I really thought about coming back but this Achilles is very damaged and if I had it done, the recovery would be so long we'd have the same outcome as this last year - everyone sitting around and waiting for me," O'Neal said. "I didn't want to let people down two years in a row. I didn't want to hold Boston hostage again. "I'm letting everybody know now so... the organisation can try to get younger talent. I would love to come back but they say once the Achilles is damaged it's never the same. I don't want to take that chance." During his 19-year career, O'Neal has played for six teams - Orlando Magic, Los Angeles Lakers, Miami Heat, Phoenix, Cleveland and, most recently, Boston.