Singh is suffering from back spasms and he is expected to be reevaluated over the weekend before determining his upcoming schedule. The injury occurred while Singh was playing table tennis with his son at their Ponte Vedra Beach home.
'I have always defended a title on the PGA Tour and I am greatly disappointed I won't be able to do so in Boston,' said Singh. 'This tournament is very special to me and I hope to return to Boston in 2006. I hope they have a great tournament this weekend. I only wish I was there.'
Singh birdied three of the last four holes to earn victory at the Deutsche Bank last year vaulting him past Tiger Woods into the No. 1 spot in the world rankings, a position that Woods has since regained.