Inconsistent Rory McIlroy remains in contention in California

The world number three carded a two-under-par 69 to stand at six under par after two rounds, four off leader Jason Kokrak going into the weekend.

McIlory might have been hoping for better after striking three birdies in the opening nine holes, but some struggles with his putter on the back nine saw him drop shots at the 10th, 13th and 15th. However, birdies on the two par fives, including the 18th, kept the Northern Irishman in contention.

American Kokrak gave himself a fine chance of earning a maiden PGA Tour title after an exemplary 64, which saw him fire eight birdies and just one bogey. He came home in five-under after a scorching back nine to finish on 10 under.

He his one shot clear of Chez Reavie, who went round in 67, with fellow Americans Dustin Johnson, Troy Merritt and Bubba Watson a shot further back on eight under.

Justin Rose finished with three birdies to propel himself up the leader board to five under but it was a bad day for first-round leader Camilo Villegas.

After starting the day on eight under after a scintillating 63 on Thursday, the Colombian needed an extra 11 shots during his second round, which started badly as he double bogied the second hole.

World number one Jordan Spieth enjoyed a better day than his opening round, but still missed the cut. Spieth carded his worst ever opening round with a 79 and he responded with a three-under 68, which included eight birdies, but it was not enough to keep him in the tournament.