Colombian Camilo Villegas holds the first-round lead at the Honda Classic in Florida, while Matt Jones was the best of the Australians.
Villegas, the 2010 champion, finished in a flurry with three birdies and an eagle on 18 to see him to a one-stroke buffer over a group of four players at six under at the PGA National Champion Course at Palm Beach Gardens.
Trailing the leader are South African Branden Grace, Canadian Graham DeLaet and Americans Rickie Fowler and Robert Streb - all on five under at the PGA Tour event.
Grace also stormed home down the back nine, as four consecutive birdies handed him some valuable momentum heading into Friday's play, while Streb matched Villegas' final-hole eagle.
There are 10 players tied at four under - seven are American - with Argentine Fabian Gomez, England's Lee Westwood and South Korea's Noh Seung-Yul the internationals among them.
Westwood went bogey-free through his first 18, while Boo Weekley impressed after going six under in the space of 11 holes after bogeying his opening two.
Defending champion and world number one Rory McIlroy began his week in underwhelming fashion to be even par in a tie for 61st place.
Under increasing scrutiny after switching his clubs from Titleist to Nike, the Northern Irishman bogeyed the 18th to be six back from the lead heading into the second round.
Course record holder and champion in 2003 Justin Leonard fared worse, carding a two-over 72, while another former winner YE Yang was well placed at three under in a tie for 16th.
Jones was the best placed of the Australians, joining Yang at three under after shooting four birdies and one bogey.
Geoff Ogilvy and Greg Chalmers (both two under) were next best, while Marc Leishman was one under at the close of play.
Steven Bowditch and Scott Gardiner were level with McIlroy at even par, while Stuart Appleby (one over), Cameron Percy (one over) and Robert Allenby (two over) all dropped shots.
Victorian Alistair Presnell was forced to withdraw through nine holes, citing illness, after he was nine over - including scoring an eight on the par-three 15th.