Nick Watney topped the leaderboard after the first round of the World Challenge in California, with European Ryder Cup hero Graeme McDowell in a chasing pack of three.
Watney shot a five-under 67 to get the better of a strong 18-man field, with four birdies after the turn at Thousand Oaks.
Portrush man McDowell was two shots back after signing for 69, including back-to-back birdies to finish his round.
Keegan Bradley, one of the most vocal defenders of the now endangered belly putter, also shot three under as did his USA Ryder Cup team-mate Jim Furyk.
Webb Simpson and Bo Van Pelt are another shot back alongside Tiger Woods, who birdied the second but struggled for fluency thereafter.
"I had a guy telling me to send my application in to Burger King for 2016" - Keegan Bradley
McDowell aside there were only two other non-Americans in the field, with Australia's Jason Day in a share of eighth on one under and England's Ian Poulter tied for 11th after carding 73.
Bradley, who has spoken up on several occasions for those who use so-called 'pivot points' with long putters, was quizzed about the joint proposal by USGA and Royal & Ancient to outlaw the technique from 2016 at the end of his round.
He revealed he had received abuse for his favoured putting stroke on Twitter and called for a greater empathy from those within the game.
"I've been catching such flak on Twitter and these other places and it would be good to kind of quiet them a little bit. I had a guy telling me to send my application in to Burger King for 2016," he told reporters at the event.
"I hope that people look at us - guys who use a long putter or belly putter - for the accomplishments and the players that we are, not look at us for using an unconventional putter.
"I feel like the USGA has really put an 'X' on our back and really shone a light on us, and I don't know if that's exactly fair.
"When we started putting with it, they were legal, and they still are. It's a sticky situation, and I hope people can see through that."