Jason Dufner struck four birdies in his final six holes to take his place with three other men at the top of the leaderboard after the opening round of the CareerBuilder Challenge in California.

The 2010 Ryder Cup player, starting on the back nine, rallied through holes four to nine to card a 64 on the Tournament Course and join Jerry Kelly, Jeff Overton and Anirban Lahiri on eight under.

Overton enjoyed a run of five successive birdies on the Tournament Course while Kelly struck five birdies and two eagles on the La Quinta course. India's Lahiri carded eight birdies in his faultless round on La Quinta.

Those playing on the Stadium Course found life much tougher, with Canada's Adam Hadwin performing best with his six-under 66 leaving him in tied eighth.

Phil Mickelson is well back on four-under after his 68 on La Quinta.