LOS ANGELES, 11 Feb 2015 (AFP) - In a statement posted on his website, Woods said the last fortnight -- which included a disastrous 82 at the Phoenix Open and a mid-round withdrawal at Torrey Pines -- had been "very disappointing."
Woods, who has plummeted to 62 in the world rankings, said the back pain that forced him to pull out after 11 holes of the first round at Torrey Pines wasn't related to the surgery he had last year and that with daily physical therapy he was improving.
But he does not know when he will tee off again in a tournament, just the latest hiccup in a turbulent career marked by marital infidelity and mounting injuries.
"Right now, I need a lot of work on my game and to still spend time with the people that are important to me," he said.
"My play, and scores, are not acceptable for tournament golf. Like I've said, I enter a tournament to compete at the highest level, and when I think I'm ready, I'll be back."
Woods, 39, said he still hoped to play the Honda Classic in Florida, which starts on February 26. That was his next scheduled start.
"But I won't be there unless my game is tournament-ready," he said. "That's not fair to anyone. I do, however, expect to be playing again very soon."
Woods, a 14-time major champion chasing the record of 18 majors held by Jack Nicklaus, carded an 82 in the second round at Phoenix on January 30, missing the cut by 12 strokes.
He endured another setback last Thursday at Torrey Pines, where his eight titles include his most recent major -- the 2008 US Open.
Woods, who could be seen grimacing and rubbing his back during the round, was two-over for the day and well off the pace when he spoke to his playing partners and walked gingerly away, hopping onto a golf cart to the parking lot and departing.
He said his back stiffened up during the morning fog delay and "just never loosened back up again."
Woods, whose world ranking is his lowest since he turned professional in 1996, said last week his back trouble felt different from the pain he dealt with early last year, when he opted for surgery to ease a pinched nerve and missed the Masters and US Open while recovering.
He made his return in June, missing the cut in the US PGA Tour's National at Congressional and finishing equal 69th at the British Open -- the worst 72-hole major finish of his pro career.
Overall, in six PGA Tour events since he returned to competition at the National, Woods has missed three cuts -- including at the 2014 PGA Championship -- and withdrawn twice.
"Next week I will practice at Medalist (Golf Club) and at home getting ready for the rest of the year," Woods said. "I am committed to getting back to the pinnacle of my game."
The first major of 2015, the Masters, will be held at Augusta National April 9-12.
Woods has won the Masters four times, but has never donned a green jacket without first winning a tournament earlier that season.