Rory McIlroy was among the early leaders as the WGC-Cadillac Championship began in Florida.
The Northern Irishman, whose Australian playing partner Jason Day withdrew at Doral with a thumb injury shortly before the start of Thursday's opening round, started with a birdie as did the other member of his group, Phil Mickelson.
Day, who won the WGC-Accenture Match Play Championship two weeks ago, cited an injured left thumb when deciding to withdraw.
He last withdrew from a tournament hurt at the 2012 Masters, due to a wrist problem.
While McIlroy found further birdies to reach three under and Germany's Martin Kaymer picked up shots on each of his first three holes, it was Jason Dufner who streaked into an early lead with a remarkable run of four consecutive birdies.
The 2013 US PGA Championship winner drove to within 14 feet of the cup on the 13th.
Mickelson tempered his opening birdie on the heavily remodelled Blue Monster course with a bogey to fall away while Graeme McDowell made amends for poor putting on the first green by holing out in three strokes on the par four second.
US Open Championship winner Justin Rose began his tournament with a birdie despite finding a bunker with his second stroke.
Dufner kept his cool to fend off a strong challenge from Ryan Moore, who began with three birdies, and he led the pack by one shot as he hit the turn.
McIlroy might have kept pace had he not mixed his four birdies with bogeys on the 14th and 17th - the first slip-up coming to pass when he missed his putt from eight feet.
Russell Henley was flawless on his way out and reached three under, but it was Patrick Reed who caught up with Dufner courtesy of four birdies in his first five holes.
Adam Scott, with a chance to overhaul Tiger Woods at the Official World Golf Ranking this week, started with five straight pars, while 14-time Major winner Woods bogeyed the fourth to be five off the lead.
