Jeff Green |
A Green, 25, was detected the lesion in a routine medical exam after signing his contract for one season and nine million dollars with the Celtics.
Doctors say that Green can fully recover and return to play professional basketball without any problem in the season 2012-2013.
An aortic aneurysm is the ballooning of the artery wall that exposes it to break and result in bleeding that can cost the life of the sufferer.
Green's contract with the Celtics will be forfeited by not having passed the examination, but the Boston club retains the rights to the player, to be operated on 9 January.