Two days after playing down concerns over his fitness, Tiger Woods was forced to withdraw from The Northern Trust ahead of his second round at Liberty National.
Woods struggled to an opening four-over-par 75 on Thursday after restricting himself to chipping and putting on the back nine of Wednesday's pro-am due to stiffness in his back.
In a statement released yesterday, the Masters champion wrote: "Due to a mild oblique strain that led to pain and stiffness, I have to withdraw from The Northern Trust.
"I went for treatment early Friday morning but unfortunately I'm still unable to compete. I'd like to thank the New Jersey and New York fans for their support and remain hopeful I can compete next week at the BMW Championship."
Speaking on Wednesday, Woods said he felt it was the "smart" approach not to hit full shots during the second half of the 18-hole pro-am, adding: "This is kind of how it is. Some days I'm stiffer than others."
The 43-year-old has played just 13 tournament rounds since winning his 15th major title at Augusta National in April, two years after he underwent career-saving spinal fusion surgery.
Woods followed a missed cut in the US PGA Championship with a top-10 finish in the Memorial Tournament and a tie for 21st in the US Open, but then took a month off before missing the cut in the Open Championship.
Speaking at the Open at Royal Portrush last month, Woods admitted he had little choice but to play a limited schedule.
"Getting myself into position to win the Masters, it took a lot out of me," said Woods, who has had four knee operations and four back surgeries during his illustrious career.
"I want to play here as long as I possibly can and you have to understand if I play a lot, I won't be out here that long."