A seven-under 65 left Rickie Fowler in a tie for third after The American Express first round.
Brooks Koepka turned to his trophy cabinet to came out on top in body banter with Bryson DeChambeau.
Four-time major winner Brooks Koepka admitted he was "hurt all year" with a knee injury that he hopes to have finally got to the bottom of.
Tiger Woods' health will be the determining factor for his success this year as he still has the game to win regularly, says Brooks Koepka.
His uncle lost his home in the Australian bushfires and Cameron Smith paid tribute to others affected after winning the Sony Open.
Cameron Smith overcame Brendan Steele in a play-off to win the Sony Open in Hawaii.
A Sunday round featuring eight birdies and an eagle saw Branden Grace secure victory at the South African Open.