American Brian Stuard fired an eight-under-par 64 to take the lead after the opening day of the Zurich Classic of New Orleans.
The 33-year-old, who is yet to win on the PGA Tour, took advantage of the rain-softened conditions at the TPC Louisiana as he carded five birdies on the front nine, including three over the first four holes.
His red-hot putting continued on the back nine as he added three further birdies to move one shot ahead of South African Retief Goosen, who had six birdies on the front nine but only one after the turn.
Australian Geoff Ogilvy and Americans JJ Henry, Derek Ernst, Patrick Rodgers and Charles Howell III carded 67s on a day when half the field did not complete the opening round after almost five hours of play was wiped out by heavy thunderstorms.
"It was just one of those days where it seemed like I was really reading the putts well and luckily they were going in," said Stuard, who was using a new putter he picked up only last week in San Antonio.
"I had a good feel for it, I putted well with it last week and it continued over today. I've been working hard at it and just needed to see some results, and today it was a good one.
"I have played well here in the past, I like the course, it seems to set it up well for me."
Australian world No 1 Jason Day raced to the turn in five-under 31 but dropped four shots on his back nine on the way to a 69, bogeying his last two holes after play had resumed following the lengthy weather suspension.
"A little frustrated," Day said of his bogey-bogey finish, "but I'm looking forward to tomorrow. I've just got to manage myself out there.
"Obviously this is going to be a bit of a tough week with the stop-and-start rounds. I might be able to sneak in nine holes tomorrow and then play 27 on Saturday. You've just got to try and stay positive and keep moving forward."
England's Justin Rose, who clinched last year's Zurich Classic of New Orleans by one shot, was among the late starters who will have to complete the opening round on Friday.