Miami - Jordan Spieth won the battle of the "Big Three" but it was Scott Piercy and Marcus Fraser atop the leader board after the first round of the Cadillac Championship at Doral here on Thursday.
The focus as the elite World Golf Championships event teed off was firmly on the marquee group of Spieth, Jason Day and Rory McIlroy - the top three players in the world rankings who are grouped together for the first two rounds.
World number one Spieth had five birdies in his three-under-par 69 that left him three shots off the lead.
Third-ranked McIlroy signed for a 71 that ended on a sour note with a double-bogey five at the par-three ninth - where he was in the water off the tee.
World number two Day settled for an even-par 72 that included four birdies and four bogeys.
He was upstaged by fellow Aussie Fraser, winner of the Maybank Championship in Malaysia a fortnight ago.
Fraser had seven birdies and was in sole possession of the lead before his only bogey of the day at his penultimate hole, the par-five eighth, dropped him into a tie for the lead with early pacesetter Piercy, who had rolled in eight birdies en route to a six-under 66.
The leading duo were one shot in front of five-time major champion Phil Mickelson.
"We all know we're trying to beat those guys week-in, week-out," Piercy said of the marquee names chasing him and Fraser. "They have proved it.
"I haven't proven it week-in, week-out," added Piercy, owner of three PGA Tour titles, "but when my game's there I'm pretty decent."
Mickelson, who has found the going difficult at Doral in recent years, had seven birdies and two bogeys in his five-under effort.
Each of his bogeys was followed by a birdie at the next hole.
"It was a good day," said Mickelson, who claimed the most recent of his 42 career wins in 2013. "I hit a lot of good shots, made some good putts and just drove it well."
Former world number one Adam Scott of Australia, who won his first title in nearly two years at the Honda Classic in Palm Beach Gardens, Florida, on Sunday, headlined a group sharing fourth on 68 that also included England's Danny Willett, Jason Dufner and Charley Hoffman.
Spieth was joined on 69 by Bubba Watson and Jimmy Walker.
Despite the benign conditions, Spieth said the tour of Doral's Blue Monster was the usual grind.
"It always is here," he said. "And this would be a day that should play about as easy as it possibly can ... Still, the scores aren't extremely low."
Leading first-round scores on Thursday in the World Golf Championships Cadillac Championship at Doral in Miami, Florida (USA unless noted, par-72):
66 - Scott Piercy, Marcus Fraser (AUS)
67 - Phil Mickelson
68 - Danny Willett, Adam Scott (AUS), Jason Dufner, Charley Hoffman
69 - Jordan Spieth, Jimmy Walker, Bubba Watson
70 - Hideki Matsuyama (JPN), Jamie Donaldson (WAL), Anirban Lahiri (IND), Rickie Fowler, Matt Kuchar
71 - Kim Kyung-Tae (KOR), Andy Sullivan (ENG), Rory McIlroy (NIR), Danny Lee (NZL), Shane Lowry (IRL), Harris English, Zach Johnson, Brooks Koepka, Henrik Stenson (SWE), Smylie Kaufman, Russell Knox (SCO), Paul Casey (ENG)