Jeff Green will have surgery to repair his aorta and will miss the season.
The 25-year-old is expected to make a full recovery.
The medical issue arose when Green was taking a physical last week. He said the problem was found when he took a stress test.
Since then, he has seen a number of specialists, the last of which was in Cleveland at the Cleveland Clinic yesterday.
Because Green could not pass the physical, the free agent contract he signed with the Celtics will be voided.
Wishing Jeff Green a successful surgery and a speedy recovery.