World number one Jason Day was forced to pick up his golf ball on the eighth hole and withdraw from the Tour Championship at East Lake on Friday, citing back pain.
Entering the week, Day was "optimistic" he could make it through the event after withdrawing from the BMW Championship two weeks ago with the same affliction.
Pundits have eyed his downswing as a probable cause for his back issues.
Day was three under for the tournament, just three shots behind the leaders, when he chose to withdraw. The injury seemingly came on the eighth hole when he chose to hit a driver out of the rough.
It remains to be seen when Day will tee up next, but it is plausible that is season could be over, thus making his next start at the 2017 opener in Hawaii.
Dustin Johnson could replace Day at the top of the rankings this weekend.