Johnson sets early pace

Zach Johnson topped the leaderboard on three under par midway through the opening day of the Northwestern Mutual World Challenge in California.

Johnson made a tremendous start at the Sherwood County Club with birdies in his opening two holes and although he bogeyed the par-four seventh, he picked up another two shots after the turn.

That left the American two shots ahead of compatriots Hunter Mahan, Steve Stricker, Matt Kuchar and Bubba Watson, and Northern Ireland's Graeme McDowell.

Former US Open champion McDowell is looking to continue his love affair with a tournament he has won twice and finished runner-up once in his only three appearances to date.

However, while McDowell matched Johnson's dream start, he was in rather more erratic form on Thursday with three bogeys and two birdies following and he is on one under par through 13 holes.

Friend, fellow Northern Irishman and playing partner Rory McIlroy, who finally claimed his first victory of 2013 in the Australian Open last week, is level par alongside world number one Tiger Woods and Webb Simpson.

It has been a rather more forgettable day for England's two entrants: Lee Westwood and Ian Poulter, who are four and five over after 12 holes respectively.