Adam Scott defied blustery conditions in Miami to move into a commanding early lead at the WGC-Cadillac Championship.
While Scott raced to eight under par at Doral, Rory McIlroy was finding his new life as World Number One hard work.
The 22 year old, who went top of the rankings by holding off Tiger Woods to win the Honda Classic last week, went to the turn in a one over par 37.
Australian Scott, who has one World Golf Championships title to his name already, covered the back nine in a brilliant 32 strokes and started the outward half eagle-birdie to go two clear of American Steve Stricker.
Woods picked up where he left off - with an eagle - but by the fifth was back to level par, while Luke Donald, who has a chance to reclaim the number one spot this week, had three birdies in his first seven holes, but bogeyed the 17th and then double-bogeyed the next after pulling his second shot into the lake.
Scott, winner of the Bridgestone Invitational last August, birdied the 12th, 14th, 16th and 17th before hitting his approach to four feet on the long first and then converting a nine foot chance at the next.
McIlroy, paired with Donald and Lee Westwood in a clash of the sport's top three, failed to get up and down from off the 11th green, sank an 11 foot birdie putt on the next, but could not save at par at the 18th after his drive finished close to the water.
Westwood had problems instantly when he thinned his greenside bunker shot to the tenth into the water. He took six there, three-putted the next and bogeyed the long 12th as well.
Spain's Sergio Garcia, playing with Woods and defending champion Nick Watney, had four birdies and bogey in his first six holes and was sharing third place with Dane Thomas Björn, Australian left-hander Greg Chalmers and Americans Charles Howell and Jason Dufner.
Scots Martin Laird and Paul Lawrie were one under after seven and five holes respectively, while Open champion Darren Clarke, England's Justin Rose and Simon Dyson, who became a father for the first time last week, and Phil Mickelson were level par.
Abu Dhabi winner Robert Rock, who could secure a Masters Tournament debut with a high finish this weekend, was two over alongside Graeme McDowell, and one further back, despite two opening birdies, came Paul Casey in his first tournament since dislocating his shoulder snowboarding in Colorado on Christmas Eve.
Scott failed to get up and down from sand on the sixth and was caught by Stricker, while Sergio Garcia was only one behind after a superb outward 31.
McIlroy just missed for eagle on the first, but then bogeyed the third and fourth - and it might have been worse.
The US Open Champion's second to the third hit the rocks on the edge of the lake, but bounced left back onto grass.
Donald, though, hit his approach to four feet there and with a second birdie in three holes was back to two under.
Scott set the target with a six under 66, but joint leader Stricker still had six holes to try to improve on that.
