Northern Ireland's Rory McIlroy said he might not play again until next year because of a long-standing rib injury.
The world number four, 28, shot a 68 to tie for 22nd in the US PGA on Sunday, and has now gone three years without a major victory.
"I don't know what I'm going to do," said McIlroy, who suffered the injury testing equipment over the winter.
"You might not see me until next year. You might see me in a couple of weeks' time. It really depends."
The US PGA was only McIlroy's 13th tournament of a season in which he has not won.
He was the pre-tournament favourite at Quail Hollow following top-five finishes in his previous two tournaments and a brilliant record at the venue, notably two wins and a course-record 61.
However, he was never in contention for a first major success since the 2014 US PGA at Valhalla.
"I can go out there and play and shoot decent scores, but when I come off the course I feel my left rhomboid going into spasm," he said.
"The inside of my left arm goes numb. I don't know what to do. I have got this next week off to assess what I need to go forward."
FedEx Cup dilemma
McIlroy's injury may end his hopes of winning the FedEx Cup - and $10m (£7.69m) in prize money - for the second year running.
He began the week 43rd in the rankings and needs to be in the top 30 to qualify for the season-ending Tour Championship in late September.
"I'm capable of playing well enough to give myself a chance in it," he said.
"At the same time, April is a long way away. That's the next big thing on my radar."
McIlroy would complete a career Grand Slam with victory in the Masters in April 2018.
He added: "I feel like I have a sense of, not duty, but I've missed a lot of time already. If I'm capable of playing, I feel like, why shouldn't you?
"But then at the same time if you are not capable of playing at your best, why should you play? It's a Catch-22."
The FedEx Cup play-offs get under way with the Northern Trust Open on 24 August, and McIlroy is the defending champion of the Dell Technologies Championship the following week.
He took six weeks off after losing out in a play-off for the South African Open in January and also missed the PGA Championship at Wentworth and the Memorial Tournament.
"We took as much time as we needed to at the start of the year," said McIlroy, who will seek the advice of sports scientist Steve McGregor in Northern Ireland in the next few days.
"It felt OK through the Masters and I switched it off for a couple of weeks because I was getting married, going on honeymoon.
"Once I started practising again, I didn't build up the volume gradually. I went from zero to hitting balls for three or four hours a day. That aggravated it a little bit.
"I just haven't allowed it the time to fully heal. I wanted to play the season. I feel like I'm capable of playing well and winning and putting rounds together.
"If I want to challenge on a more consistent basis, I need to get 100% healthy. I want to get back into that winner's circle."