Brian Gay birdied four of his first six holes and deftly shook off a "hiccup" of a double bogey to finish with a 66 that left him one shot off the lead.
Gay started on the back nine and made consecutive birdie putts of 7 and 22 feet. Then he rolled in a 12-footer at the par-5 13th and missed an ace at the 15th by two inches.
He moved to 5 under with a 2-footer for birdie at the first hole. But Gay found the trees to the left side of the fairway at No. 6, chipped out, hit his third shot into the greenside bunker and fourth on the green before two-putting from 15 feet for the double.
Undaunted, Gay responded by holing a bunker for for birdie at No. 7 and making a 20-footer for birdie at No. 9 to polish off the 66. It was his best opening round since he tied for 16th at the AT&T Pebble Beach National Pro-Am in February.
"The course is really, really wet," Gay, who ranks 51st in the FedExCup, said. "The ball is plugging in the fairway, the greens are soft. Pretty smooth early, though, not too much traffic. Getting pretty beat up during the day. But good solid start."