Rory McIlroy might not play again in 2017 as he continues to struggle with the injury which has limited him to 13 events in a winless season, his third in succession without a major title.
McIlroy came into the US PGA Championship as the pre-tournament favourite on the back of top-five finishes in his last two starts and a brilliant record at the host venue of Quail Hollow, including two wins and a course record of 61.
However, the 28-year-old was never in contention for a first major victory since the 2014 US PGA at Valhalla and completed a closing 68 before the final groups teed off in round four.
Asked after his third round how far off his best he was following a year which has included a serious injury, a change of equipment, his wedding and a split from long-term caddie JP Fitzgerald, McIlroy simply replied: "Looking forward to 2018."
And speaking on Sunday, the 28-year-old expanded on his dilemma about playing again this season or trying to win the FedEx Cup - and USD10million bonus - for the second year running.
" I don't know what I'm going to do," said McIlroy, who suffered the rib/back 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.
" I have upped my practice coming into these two events because I wanted to feel like I was in a good place in my game. 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.
"The inside of my left arm goes numb. So I don't know what to do. I have got this next week off to assess what I need to go forward."
McIlroy began the week 43rd in the FedEx Cup rankings and needs to be in the top 30 to qualify for the season-ending Tour Championship in late September.
The play-offs get under way with the Northern Trust Open on August 24 and McIlroy is the defending champion of the Dell Technologies Championship the following week.
However, he already has one eye on next April's Masters, which he needs to win to complete the career grand slam.
" I feel like I'm capable of playing well enough to give myself a chance in it," McIlroy said of the FedEx Cup. "At the same time, April is a long way away. That's the next big thing on my radar.
" 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."
McIlroy took six weeks off after losing out in a play-off for the South African Open in January and also missed the BMW PGA Championship at Wentworth and the Memorial Tournament.
"I felt like we took as much time as we needed to at the start of the year," McIlroy, who wi ll seek the advice of sports scientist Steve McGregor in Northern Ireland in the next few days, added.
"I t felt okay through the Masters and I switched it off for a couple of weeks because I was getting married, going on honeymoon. Then 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 per cent healthy.
" It's tough (to go three years without a major). I want to get back into that winner's circle. You don't want to be teeing off at 9:45 in the final rounds of a major on a Sunday. That is not where you want to be."