Steven Bowditch has carded an eight-under-par 62 to take the outright lead after day one of the AT&T Byron Nelson Championship in Texas.
The Australian, 31, sank no fewer than eight birdies in a glittering bogey-free opening round in Irvine to set the pace ahead of Friday's session.
Bowditch sits two strokes clear of Jimmy Walker on six-under, while James Hahn and Ryan Palmer are one shot further back.
Keegan Bradley, who won the PGA Championship in 2011, is one of three players with a four-shot deficit to make up, along with Tom Gillis and John Merrick.
Defending champion Brendon Todd shot a two-over-par 72, while Rory Sabbatini, whose combined winning score of 261 in 2009 remains a tournament record, is seven shots off Bowditch.
