Rory McIlroy finished three shots off the pace in the first round as he made his debut at the AT&T Pebble Beach Pro-Am.
The 28-year-old carded an opening round of four-under 68 to leave him chasing current leaders Kevin Streelman and Beau Hossler.
McIlroy had shot five birdies and one bogey to leave him four-under after 15 holes of the Spyglass Hill course, before a wayward drive gave him another bogey on the 16th.
But the four-time major winner rallied to hole a birdie on the 18th and remain among the chasing pack.
American Streelman and compatriot Hossler, a PGA Tour rookie, shared the top spot after both finishing on seven-under 65 on different golf courses.
Streelman shot seven birdies - including one on the final par-4 18th hole - at Spyglass Hill, while Hossler carded the same, with a spectacular 54-foot putt for birdie on the par-4 16th hole at Pebble Beach.
Dustin Johnson carded a five-under 67 opening round as he bids to hold on to his position as world number one, while Graeme McDowell finished at one-under 71 after double-bogeying the 17th hole.
It was a disappointing day for defending champion Jordan Spieth, however, who had to settle for a round of 72 on the Monterey Peninsula course, making one birdie, one bogey and 16 pars.