Woods, ranked No. 1 in the world, the winner of five tournaments this year and the leader in the FedEx Cup points race, said prior to last week's playoff opener in New Jersey that he was playing with a stiff back.
Late in each round of the rain-marred tournament Woods showed signs of discomfort and in the final round he fell to his knees when a back spasm caused him to hit a ball into the water at the 13th hole of the Liberty National Golf Club course.
Despite the pain, Woods recorded two late birdies and came within an inch of holing a birdie putt on the final hole that would have put him in a playoff with eventual winner Adam Scott.
Woods played a practice round Thursday at the TPC-Boston layout and said he was "pleasantly surprised" he was able to hit pain-free shots.
Although he said he was not looking forward to it, he will receive daily treatment on his back for the foreseeable future.
The top 100 point earners in the year-long competition will play this week and only the top 70 at the end of the week will move on to the third playoff event.
Tim Clark will be in 100th place at the start of the tournament and to climb into the top 70 he will likely have to finish no worse than 25th in this week's event.
Woods is followed by Scott and Phil Mickelson in the points chase and they will make up the feature threesome during the s first two days.
The winner of the FedEx Cup, who will be crowned at the Tour Championship in Atlanta on Sept. 22, will receive $10 million.
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