R1 LEADERBOARD US unless stated -10 T Lehman -9 Dean Wilson -8 Arron Oberholser -7 Tom Pernice, Ernie Els (SA), Dudley Hart Selected others -4 Luke Donald (GB) -3 Tiger Woods, Sergio Garcia (Sp), Bernhard Langer (Ger) -1 Vijay Singh (Fij) Level Phil Mickelson

Lehman fired 11 birdies on the north course, seven in the back nine, to lead Dean Wilson who had a bogey-free 63.

Arron Oberholser is a shot further behind in third while South African Ernie Els is in a group with Tom Pernice and Dudley Hart on seven under.

Tiger Woods is on three under while Vijay Singh is two shots further back.

Phil Mickelson, playing his first event of the year, had two bogeys and two pars for a level-par 72.

It was not the best day for Mickelson, who started well with a birdie at the first but was only hit five fairways in total.

Britain's Luke Donald fired a 68 to end the day on four under, six shots off the lead.

The event is played over two courses at the Torrey Pines Country Club with one round at the easier north course and three, including the final two rounds, at the harder south course.

Of the top 17 scores, 15 came from the north course.

Lehman took full advantage of the easier set-up and birdied his last six holes to lead the field.

"I'm doing a lot of things right that you need to do right out here," said Lehman.

"It would have been nice to continue to the first tee on the south course and keep going."

Although Els played some sloppy shots on the north course, he was able to fire nine birdies in his 65 with five coming in his first five holes.

Woods, who has been struggling with flu, twice saved par with long putts but was happy to end up under par.

"I'm grinding out there. I don't have the skills that I normally do, but I've just got to go out there and just try to survive and hopefully feel a little better and hopefully get stronger each and every day."