FedEx Cup hopeful Jordan Spieth acknowledged he is not in control of his own destiny after falling behind Paul Casey at the Tour Championship.

Spieth entered this week's Tour Championship leading the FedEx Cup standings. Now, with one round to play, the three-time major winner stands as the third-most-likely to claim the coveted trophy.

A third-round 69 on Saturday left Spieth four under through 54 holes, eight shots adrift of leader Casey, who is poised to win the FedEx Cup ahead of Justin Thomas and the former world number one.

While Spieth still has a chance to clinch the FedEx Cup without winning at East Lake, the American star said: "Unfortunately, I'm not really in control of my own destiny at this point.

"But I'll go out tomorrow [Sunday], try and shoot a really solid round of golf and then do some cheerleading."

Spieth added: "I know that I'm capable of going low on this golf course, it's a matter of hitting fairways, it's a matter of getting the ball in the hole on the putting green and neither one of those has been a strength this week unfortunately, but one day to go."

On Sunday, Spieth will tee off alongside world number one Dustin Johnson – who is fourth in the race for the FedEx Cup.