Bryson DeChambeau was second on five-under.
Among the Australians, Adam Scott’s best opening round at the Masters in five years had the 2013 Augusta National champion sitting on three-under-par 69.
Scott had not broken par on Thursday at the April major since the 2014 edition but birdied the final two holes and briefly shared the clubhouse lead with South Africa’s Justin Harding and Jon Rahm (69).
Scott was treading water at even par through 14 holes but surged up the leaderboard to two under courtesy of birdies at the par-five 15th, the difficult par-four 17th and the last hole.
Australian Jason Day, meanwhile, is currently tied with Scott at three under after 17 holes.
It is reported Day aggravated his chronic back injury by picking up one of his children on Thursday morning although that hasn’t been confirmed.
Queenslander Cameron Smith is only one shot behind, having posted a 70.
Smith birdied three of his last six holes to finish two under after a sloppy start.
Also at two under is Tiger Woods, with the four-time Masters winner building a hot round before a par on the par-five 15th and a bogey at the 17th cruelled his momentum.
Smith was well versed about Augusta National’s course changes ahead of the 83rd Masters but Thursday’s pin placements took the Queenslander by surprise.
‘‘The pin on the 14th was a ripper; that was a pearler,’’ he told reporters.
‘‘There were some tough pins out there; couple took me by surprise.’’
‘‘The scores weren’t great and it was tough out there; if you don’t have your best stuff like I did [Augusta] can be brutal,’’ Smith said.
‘‘Could have let it get away from me a little bit but I hung in there and put a nice swing on a few shots coming home.’’
A year after finishing as the top Australian in a tie for fifth, Smith is well in contention going into the second round.
‘‘It’s nice to know I can still scratch out a score even without my A game,’’ he said.
‘‘I made plenty of clutch putts and sometimes you have to scrap a score out there and hopefully I can continue that the rest of this week.’’