Scottie Scheffler held onto a four-stroke lead despite second-round charges from Collin Morikawa and Xander Schauffele at the Tour Championship.
The world number one went into the second round at East Lake with a seven-stroke advantage, courtesy of an opening 65 and a two-shot starting cushion after finishing top of the season-long FedEx rankings.
Two late birdies after a delay for thunderstorms ensured he kept much of his advantage, a 66 taking him to 21-under-par.
"I feel like my swing is in a good spot. I've hit it nice last couple days," Scheffler said. "A lot of quality stuff out there, and yeah, in a good spot going into the weekend."
Morikawa also finished strongly as the closing groups resumed their round, finishing with two of his nine birdies in a round of 63 which lifted him to 17-under-par.
Open and USPGA champion Schauffele is a further shot back after also grabbing a birdie on the last in a bogey-free 64
Sahith Theegala, Wyndham Clark and Adam Scott are four shots further back on 12-under-par.
For the second round running, Rory McIlroy and Shane Lowry both carded rounds of 69 to sit at eight-under and seven-under respectively after Day 2.
A long 25-foot birdie putt at the fourth and a tap-in birdie at the sixth had McIlroy out in 33. He briefly moved to nine-under following another birdie at the 14th, but his sole dropped shot at the day arrived at the 16th as he found sand off the tee.
Lowry went wild right on the first, ultimately finishing with a double bogey, but he wouldn't drop another shot with four birdies completing his card.
