Before the Buick, Woods had not won a strokeplay title since 2003

The 29-year-old American lost the top spot to Vijay Singh in September but the Fijian's absence from the Los Angeles event opens the door.

"Tiger needs to pick up 19 world ranking points at the Nissan Open to overtake the Fijian," said world rankings organiser Ian Barker.

"He has to finish no worse than fourth or in a three-way tie for third."

Woods has not won the Nissan in nine attempts but has enjoyed four top-10 finishes at Riviera, including a runner-up spot in 1998 and a tie for second in 1999.

His task will be made easier as world number three Ernie Els and world number four Phil Mickelson, winner of the last two PGA Tour events, are also missing.

Woods, back after a three-week lay-off since winning the Buick Invitational, had enjoyed a five-year reign at the top of the rankings.

And he insisted Riviera was a course which should suit his game.

"I played in my first pro event there when I was 16 and have great memories of the course," said Woods, who will also be bidding to extend his record run of 135 straight PGA Tour events without missing the cut.

"I love old, traditional layouts that require shot-making, smart play and good touch - and you need all three to win at Riviera."

Canada's former Masters champion Mike Weir, the world number six, is bidding to win the Nissan Open title for the third year in succession.

A strong European contingent will also be competing in California, including Lee Westwood, Ian Poulter, Brian Davis, Colin Montgomerie, Darren Clarke, Luke Donald and Justin Rose.

World ranking points are accumulated over a two-year period, with double points awarded in the most recent 13-week spell.

The points are weighted according to the status of the event and strength of the field.