The world number one will look to complete the WGC grand slam having won the WGC-Match Play in 2015, the WGC St. Jude Invitational in 2014 and WGC-Champions trophy last year, with the competition due to reach a climax on Sunday (February 23). 

By the end of hole nine, he was three under par with four birdies and one bogey, closely followed by England's Paul Casey and the United States' Bubba Watson.

The second-half of the 18 started promising after scoring an eagle on hole 11, with a birdie on the 15th bringing his total to six under par.

Watson stayed consistent to score birdies on the 13th and the 18th to go four under alongside fellow American Justin Thomas who putted for two late birdies to finish level.

Four golfers sit in fourth on three under including South Africa's Louis Oosthuizen and America's Billy Horschel, who had a yo-yo first day with three bogies and six birdies, keeping him three from the top of the leaderboard.

Spain's world number three Jon Rahm sits one over after a nightmare second half, going three over par after two birdies in the first nine holes.

World number five and reigning champion Dustin Johnson also struggled after a double bogey in the 12th added to his misery as he sits 11 shots behind McIlroy.