Jason Day has been struck down by an injury that threatens to derail his pitch for the Fedex Cup in the United States.
Day withdrew from the final round of the BMW Championship at Crooked Stick, Indiana, today after playing eight holes.
The Queenslander tweaked his lower back when he bent down to put a tee in the ground on the ninth tee and decided to pull out rather than risk further damage.
The Australian has a history of back issues, withdrawing from the BMW Championship in 2014 with a similar complaint.
He almost withdrew from both The Barclays in 2015 and the World Golf Championships Match Play this year with the same issue before fighting through the pain and winning.
While the move was mostly precautionary, he will enter East Lake under an injury cloud.
“He's all right, he's just got some back issues and is in a little bit of pain,” Day’s manager Bud Martin said.
"He's getting treatment right now. I don't think it's anything that he hasn't dealt with before.
“The trainer is maybe thinking it's the same type of thing that he dealt with at The Barclays and last year where he picked something up in his bus and it kind of got out of line.
“But just better safe than sorry.
"Instead of forcing it, we just decided that it was more prudent to kind of come in, get it worked on, and deal with it.”
Martin would not speculate whether Day would be at full strength for the finale of the FedExCup playoffs.
Day started the week at No. 2 on the FedExCup points list, but although he dropped to No.4, is still in the all-important top 5 headed to East Lake.
Any of the top-five ranked players can win the playoffs with a victory in Atlanta.
They suggested the move was precautionary, since he was out of contention anyway and still more than likely to remain in the top five on the Fedex Cup rankings for the Tour Championship in Atlanta the week after next.
Day has had a plethora of illnesses and injuries in the recent past from vertigo to wrist issues.
But he remains the No. 1 player in the world, albeit under threat from world No. 2 Dustin Johnson.