|Farmers Insurance Open first round leaderboard|
|-8 N Thompson (US); -7 M Thompson (US); -6 C Tringale (US), B Koepka (US); -5 J Vegas (Ven), F Jacobson (Swe), B de Jonge (Zim), C Campbell (US), C Kirk (US), I Poulter (Eng); Selected others: -3 L Donald (Eng), P Harrington (Ire); +1 P Mickelson (US); Withdrew T Woods (US)|
Tiger Woods has withdrawn from his latest tournament - the Farmers Insurance Open at Torrey Pines - because of more back problems.
The 14-time major champion was two over par when he abandoned his first round after just 11 holes.
The 39-year-old American spoke to his playing partners before walking off the course and into a waiting car.
His early departure comes after he shot a career-worst 82 in the second round at Phoenix last week.
Woods was playing in only his second tournament of the season after returning from surgery on a pinched nerve, which forced him to miss last year's Masters and US Open.
He appeared to hurt his back after hitting his tee shot at the 12th - his third hole of the day - but carried on for eight more holes.
His struggles were made more evident when playing partners Rickie Fowler and Billy Horschel both helped him pick his ball out of holes.
In a brief word with reporters, Woods said his lower back got tight during a fog delay that suspended play for more than two hours.
"My glutes keep shutting off and that causes me pain in my back," he said. "It got worse as we stood waiting on the putting green during the delay and I tried warming up my glutes, but it just wasn't working for me.
"When we went back out, it just got progressively worse."
American Nicholas Thompson hit an eight-under-par round of 64, featuring seven birdies, an eagle, and a bogey, to take a one-stroke lead over compatriot Michael Thompson after the opening round.
England's Ian Poulter leads the British charge, lying in a tie for fifth place on five under, three shots behind the overnight leader, while 2013 Open champion Phil Mickelson was one over par through 15 holes when fog halted play for the day.