New father Rory McIlroy boosted his chances of becoming the first back-to-back winner of the Tour Championship after a brilliant opening round in Atlanta.
McIlroy, who celebrated becoming a father for the first time with the birth of daughter Poppy on Monday, started the week seven shots off the lead under the controversial handicap system adopted last year.
However, the four-time major winner reduced his deficit to four strokes thanks to a superb 64 which included eight birdies and two bogeys and a back nine of 30 at East Lake.
FedEx Cup leader Dustin Johnson saw his two-shot lead wiped out despite an opening 67, with playing partner Jon Rahm carding a 65 to join world No.1 Johnson on 13 under par.
Justin Thomas is two shots off the lead on 11 under following a 66, with McIlroy on nine under and Mexico's Abraham Ancer seven under after matching McIlroy's 64.
Marc Leishman is best of the two Australians but is eight shots adrift of Johnson and Rahm despite a four-under 66.
Leishman is in a tie for 10th with Cameron Smith in equal 18th after an opening round two-under 68.
McIlroy said he didn't have time to think about how he might get himself back into contention.
"It could be the secret, turn up the afternoon before you're supposed to tee off and play a quick nine holes and see where your game's at," he said after only travelling to Atlanta on Thursday.
"At the start of the week golf was the furthest thing from my mind and sometimes that's a good thing. Sometimes it's nice to get away from it and it sort of puts things in perspective a little bit.
"I was coming here with not many expectations.
"I played OK last week but still struggling in comparison with how I played earlier this year so sort of coming here with a load off my mind that Erica's great and Poppy's in good health so I could just concentrate on golf and it was nice to shoot a good first round."