Rory McIlroy admits his game "isn't where it needs to be" after his T34-finish at this weekend's Northern Trust at Glen Oaks Club.
McIlroy was 15 shots off the pace set by Dustin Johnson and Jordan Spieth, with his final-round 72 leaving him two over for the tournament.
World number one Johnson recovered from five shots down to beat fellow American Spieth at the first sudden-death hole to win the tournament, the first of four PGA Tour FedEx play-off events.
Johnson, who won three consecutive starts before a back injury ruled him out of the Masters, joins Justin Thomas as a four-times winner on the PGA Tour this season.
McIlroy, who began the four-tournament season-finale FedExCup 44th in the standings, needs to finish in the top 30 to gain entry to the Tour Championship.
The golfer with the most points at the end of Tour Championship wins the FedExCup and a US$10m bonus.
The world number four, who has already confirmed that he will take a three-and-a-half month break after the Dunhill Links event in Scotland in October to rest persistent rib and back injuries, admits he is struggling for form and fluency.
"My game isn't where it needs to be," McIlroy said.
"But it's okay, conditions were tricky out there. This afternoon the course played quite firm and fairways were bouncing out a lot.
"Again, my battling qualities, that's all I really have right now. I'm sort of a little inconsistent with my swing and sort of with everything else.
"It's just a matter of trying to go out there and put the best possible rounds together and see where that leaves me."
The FedEx play-offs continue with the Dell Technologies Championship between 1-4 September, the BMW Championship [14-17 September] and the Tour Championship [21-24 September].