That leaves the open champion in a tie for 32nd.
Shane Lowry carded an even par round of 72 to begin his challenge at the CJ Cup in Las Vegas overnight.
The Clara golfer had a mixed card of five birdies, three bogeys and a double bogey, leaving him in a tie for 32nd.
That's seven shots off the leader and winner of last week's BMW PGA Championship at Wentworth Tyrell Hatton, who's 7 under.
Rory McIlroy struggled towards the end of his round.
The world number four bogeyed his final three holes as he signed for a one-over-par 73 in Las Vegas - which leaves him in a tie for 37th.