Adam Scott was the only Aussie to hold his ground on moving day, but the former World No.1 remains three over for the championship and eight shots off the pace after posting an even-par 73.

Scott bagged five birdies but also made five bogies to be sharing 37th spot late in the day at the year's third major in San Diego.

Wade Ormsby made a promising start with two birdies in his first three holes but faded to card a 73 and be four over, nine shots adrift of leaders Louis Oosthuizen (70), Mackenzie Hughes (68) and Russ Henley (71).

Marc Leishman was a further two back following a round of 75 that started with a double-bogey six on the 1st hole and never improved.

Matt Jones was the leading Australian entering the round but was the worst performer of the day.

Jones racked up seven bogies and a double for a 79 to tumble to nine over.

Jones made seven bogies in his opening 14 holes. PHOTO: Sean M. Haffey/Getty Images.

Some of the game's biggest names were the biggest movers on Saturday.

Defending champion Bryson DeChambeau and four-time major winner Rory McIlroy share fourth spot just two shots behind the leaders.

DeChambeau posted a bogey-free three-under 68 while McIlroy matched the day's best round with a 67.

World No.3 and pre-tournament favourite Jon Rahm (72) shares sixth place at two under with Americans Scottie Scheffler (70) and Matthew Wolff (73).

World No.1 Dustin Johnson stormed into red figures with a 68 to be one under and tied ninth with fellow Americans Xander Schauffele (72) and 2020 US PGA Championship winner Collin Morikawa (70).

Two-time US Open champion Brooks Koepka and World No.2 Justin Thomas round out a star-studded leaderboard at even par after carding 71s.

- Darren Walton, Australian Associated Press