Four-time Major winner Rory McIlroy ended the first round of the Northern Trust Open in California four shots off the lead after carding four-under-par 67 on Thursday.

The Irishman, who is making his first appearance in this tournament, secured five birdies, but dropped a shot on the 15th hole.

Camilo Villegas has taken the clubhouse lead having carded eight-under 63 in the first round, which included nine birdies, four of which came on consecutive holes, and a solitary bogey.

Americans Chez Reavie, Bubba Watson and Luke List sit three shots off the pace with first-round 66s, while Ricky Barnes matched McIlroy by finishing the day four-under-par.

World number one Jordan Spieth had a torrid round having made eight bogeys and a double bogey on the 18th, which left him third from bottom in the field with an eight-over 79.

The score is the worst that Spieth has ever recorded in a first round of a tournament in his professional career.