Graeme McDowell sits three shots off the lead after the opening round of the AT&T Pebble Beach Pro-Am in California.
Playing at the venue where he won the 2010 US Open, McDowell carded a 68 to finish at four-under par alongside ten other players in a round that included four birdies, but he will be disappointed with a bogey at the last.
Shane Lowry is the other Irish competitor in the field and he opened with a 71 to lie on one under.
Brian Gay produced an impressive birdie run to take a share of the first-round in California.
The American got to five under at the turn thanks to five straight birdies from the fifth on the Monterey Peninsula course and had just one blemish on the back nine to fire a seven-under par 64.
Countryman Scott Langley, starting on the back nine, birdied half his holes on the same course, including one on the par-three ninth, to join Gay at the top of the leaderboard.
Five-time major champion Phil Mickelson sits one shot off the lead after making five birdies on the back nine for a 65 as he hit every fairway in a PGA Tour round for the first time since 1998.
He was matched by former world number one Jason Day, who had just one bogey on the par-four 15th before recovering with three birdies in a row.
The tournament is played over three courses - Monterey, Pebble Beach and Spyglass Hill - before the final round at Pebble Beach on Sunday.