Bubba Watson has broken into the world's top-20 on the back of his one-stroke success at the Farmers Insurance Open over the weekend.

The big-hitting left-hander has climbed 15 spots to number 18 in the world rankings after holding off Phil Mickelson to triumph by a single stroke at Torrey Pines.

Watson's nerveless 12-foot breaking putt for birdie at 18 was enough to seal victory, leaving Mickelson the improbable prospect of having to hole out from some 72 yards to force a play-off.

Despite a wonderful attempt, he was unable to do so, but there was some consolation for Mickelson who moved back above Steve Stricker and Graeme McDowell to reclaim the No.4 spot.

Paul Casey's triumph at the Volvo Golf Champions event in Bahrain has seen edge up three spots to six in the world, behind Lee Westwood, Martin Kaymer, Tiger Woods, Mickelson and McDowell.

Neither Westwood or Kaymer were in action last weekend, Woods was but could only manage tied 44th at Torrey Pines and could soon slide further down the rankings if his results don't improve.