There are equations, calculations and a multitude of different scenarios but for the three Australians vying for the 2018 FedEx Cup title there is a universal truth that remains; they must win the Tour Championship.

Cameron Smith (10th), Jason Day (12th) and Marc Leishman (29th) all enter the PGA Tour’s FedEx Cup finale as mathematical chances of claiming the $US10 million awarded to the FedEx Cup champion but only if they can first best the 30-man field at East Lake Golf Club in Atlanta.

For Smith to cash in on the FedEx Cup bonus – a prize that will grow to an astonishing $US15 million for the winner next year – he would need to win the tournament and then hope that leader Bryson DeChambeau finishes in a three-way tie for worse, second-placed Justin Rose finishes tied for third or worse and Tony Finau, Dustin Johnson and Justin Thomas all finish tied for second or worse.

“A lot of stuff is going to have to go my way as well to get my hands on the big trophy,” Smith said of his FedEx Cup prospects.

“I’m just going there and trying not to think about it too much.  Just go there, treat it as a normal golf tournament and do my prep and hopefully everything falls my way during the week.

“I’m just preparing as if it’s another Tour event, just put in everything I can and if it happens, it happens.”

Although the initial part of the equation – win the tournament – remains the same for Leishman, the Victorian would need a veritable house of cards to miraculously fall into place, quipping with his Australian World Cup partner this week: “You’ve got a lot more chance than I do.”

“I’m pretty much going there not even thinking about the FedExCup, just thinking about trying to win the tournament,” said Leishman, who at the very least would need DeChambeau to finish 28th or worse to even be a chance.

“It’s basically zero that I’m going to win the FedExCup, but there’s still $9 million and a trophy at the end of the week.

“I’m going to go there and have the best week I can have, try and walk away with a trophy, and hopefully Cam can play good and walk away with the FedExCup.”

Australia’s most accomplished player on the PGA Tour this year with two wins, Day said that he will deem 2018 a “disappointing” unless he can triumph at East Lake.

In order to claim the FedEx Cup Day would need to win and have DeChambeau finish tied for sixth or worse, Rose finish tied for fourth or worse and Finau, Johnson and Thomas to all finish outside the top two.

“This year, even though I’ve had two wins, has been disappointing,” Day told AAP.

“I didn’t play good in the majors and I could have played a lot better in the first three playoffs.

“Winning the FedEx Cup and the Tour Championship would definitely sway that feeling.”

Smith is making his debut at the Tour Championship while Day’s best finish at East Lake was a tie for fourth in 2014 and Leishman was tied for 24th in his Tour Championship debut last year.