Miami - Australia's Jason Day withdrew from the Arnold Palmer Invitational on Thursday citing a back injury.
The 31-year-old walked off the course after playing his second shot on the 16th hole after teeing off on the back nine at Bay Hill Club in Orlando, Florida.
Day later revealed he had been struggling with a sore back last week and underwent an MRI scan on Monday which indicated a tear in a disc.
"I saw a physio here (in Orlando) and tried to do as much work as I possibly could to get ready for this week," the world number 11 said.
"I couldn’t play at 100 percent today, so I just wanted to see if I could get out here and my back may have loosened up. But, unfortunately, it didn't, so I had to pull out," said Day, who was two-over when he withdrew.
Day said he still aims to recover in time for next week's Players Championship at TPC Sawgrass.
Asked by GolfDigest.com if he intended to compete at the Players, he replied: "I'm going to try."