Rory McIlroy wiped off a three-shot deficit to Billy Horschel to share the 54-hole lead with the American at the Tour Championship.
Horschel held a healthy buffer on the back nine at East Lake Golf Club on Saturday, leading world number one McIlroy by three in the race for the $10million FedEx Cup bonus.
But McIlroy sunk a 26-foot eagle putt at the 15th, after Horschel bogeyed the par-four 13th as the pair finished the day at nine-under-par overall.
Horschel carded a one-under-par 69 to follow on from consecutive 66s, while McIlroy ended the day with a 67.
American Jim Furyk is outright third, two shots back after a round of 67 that featured three birdies in his final seven holes as he finished in a flurry.
While McIlroy and Horschel will win the FedEx Cup if they win the season-ending tournament, Furyk can also bag the cash bonus - if he wins the tournament, and Horschel and Chris Kirk finish in ties for second or worse.
Tied for fourth are Rickie Fowler (67), Justin Rose (66) and Jason Day (70) on six under, while tied for seventh are Kirk (71), Ryan Palmer (69) and Russell Henley (67).
Australia's Adam Scott bounced back from a second-round 72, firing in seven birdies as he posted a 65 to be outright 10th - five shots off the pace.
American Bubba Watson is 11th, improving six shots from rounds two to three as he carded a 67 to be three-under-par overall.
Watson is one of five players who are assured of the FedEx Cup with a win in Atlanta, Georgia, along with McIlroy, Kirk, Horschel and Hunter Mahan (71).
Mahan, though, is the only player of the quintet out of contention, as he sits tied for 25th in the 29-man field on seven-over-par.