Fiji's Vijay Singh took advantage of stumbling finishes by Jim Furyk and Anthony Kim to win the Chevron World Challenge by one shot.
Singh was two strokes off the lead going into the final day but he birdied four of the last eight holes for a closing 68 which put him on 11 under.
Overnight leader Kim carded a 73 for third while Furyk dropped four shots in the last three holes to finish fifth.
Steve Stricker claimed second in California with a closing 68.
England's Luke Donald fired the lowest round of the week at Thousand Oaks, a final-round 66 lifting him into eighth place on level par.
Kim and Furyk battled it out at the top of the leaderboard during the opening nine holes before Singh and Stricker played themselves into contention from the turn.
"I don't know if I can keep doing this for another four, five or six years but I'm going to try"
The American drew level at 10 under with a birdie at 13 but his title challenge unravelled with bogeys on 14, 16 and 17, as well as a double bogey at the last, while Kim fell even further behind after double bogeying 14 and 15.
Stricker birdied the par-three 17th to join Singh in a share of the lead but the Fijian struck a superb six-iron into the heart of the 18th green before rolling in an eight-foot birdie putt to seal his fourth victory of the year.
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"It was very unexpected," said the 45-year-old. "I just hung in there. I thought Jimmy Furyk was playing so well and Anthony, so I just had to keep pace.
"My thought was if I shot a 67 or 68 I may have a good chance and it ended up being what I needed.
"When I show up and I know I can't win the golf tournament, I'm going to quit. But as long as I show up and know that I can win, I'm going to keep playing.
"I don't know if I can keep doing this for another four, five or six years but I'm going to try."
The event, which is hosted by Tiger Woods and benefits his foundation, featured a 16-player field.
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