Atlanta: Besides the $10 million playoff bonus prize on offer at this week's season-ending Tour Championship at East Lake Golf Club, the world number one ranking held by Australian Jason Day is also at stake.
New world number one Day, who ascended to the top of the rankings with his victory at last week's BMW Championship, can only lose his position if either Jordan Spieth or Rory McIlroy win the tournament, world rankings officials said on Friday.
Should third-ranked American Spieth win the Tour Championship, he will return to number one if Day finishes outside the top five at East Lake.
Should second-ranked Northern Irishman McIlroy triumph, he will reclaim the number one spot if Day is outside the top 15 in the PGA Tour's season-ending tournament.
Day, of course, could make it all academic by winning the 28-man event that concludes the FedExCup playoffs himself, a victory that would also bring the world number one the $10 million that goes to the overall points leader on the list.
The fascinating back-and-forth at the top of the rankings has so far continued for five successive weeks with a different person occupying the top spot.
Spieth and McIlroy traded places for four straight weeks before Day took over at the top on Monday.