Jason Dufner rolled in a 30-foot eagle putt at the 18th hole on Friday to cap a seven-under 65 and take a one-shot lead after two rounds of the US PGA Tour Zurich Classic.
Dufner, seeking to break through for a first US tour title, also had five birdies in his bogey-free effort at TPC Louisiana and took a 12-under total of 132 into the weekend.
The American was one shot in front of Scotland's Russell Knox, John Rollins and Ken Duke.
Knox matched the course record with a 64, Rollins a 66 and overnight co-leader Duke a 68 for 133.
Australian Greg Chalmers holed out from 137 yards for an eagle on the par-four first en route to his 64, which saw him join South African Ernie Els (68) and Steve Stricker (68) on 134.
Defending champion Bubba Watson, making his first start since winning his first major title at the Masters, posted his second straight 71 to make the cut by a stroke.
World number two Luke Donald of England bounced back after a disappointing first-round 73 with a 65 for 138.
Donald also holed out from the fairway at the first hole.
Dufner launched his round with a three-foot birdie at the first. He birdied three in a row from the fifth and added another at the par-five 11th.
Knox, a graduate of the Nationwide developmental tour who is making his ninth PGA Tour start, had seven birdies and an eagle at 18 with one bogey.
US veteran Stricker pulled level with Dufner with four straight birdies from the seventh, but missed a two-foot birdie putt at 11 and gave back two strokes with bogeys coming in.