Jason Day has become an injury doubt for next week’s Players Championship after withdrawing mid-round from the Arnold Palmer Invitational.
The Australian, a former winner in both events, only completed six holes of his opening round at Bay Hill before walking off the course with a back injury.
Day told Golf Channel that he had taken medication for a sore back while practicing at TPC Sawgrass last week ahead of his bid for a second Players Championship title, only to see the pain worsen over the weekend.
"I woke up Sunday and I couldn't really walk," Day said. "Couldn't sit in a car, it was really difficult.
"I ended up coming down here [Arnold Palmer Invitational] and seeing a physio and trying to do as much work as I possibly could to get ready for this week. It just wasn't going to work out."
An MRI scan on Monday revealed an annular tear in the disc between his L4 and L5 vertebrae along with additional "facet problems", with Day unable to play a practice round prior to his early tee time on Thursday with Rickie Fowler and Ian Poulter.
Day failed to get up-and-down from a greenside bunker to save par at the 10th - his opening hole - and found water on his way to a double-bogey at the par-four 13th.
The world No 11 holed a 15-footer to birdie the 14th and made par on his next hole, only to cut short his round after putting his approach at the par-five 16th into the water.
"I couldn't play at like 100 per cent today," Day added. "I just wanted to see if I got out here and it may have loosened up, but unfortunately it didn't.
"It [whether he will be fit to play the Players Championship] is too early to tell right now. I think it's just rest, to be honest, and hopefully I'll be ready by next week."
Watch the Players Championship throughout the week live on Sky Sports' dedicated channel - Sky Sports The Players.