(CNN) -- Steve Stricker will take over from Phil Mickelson as world number two after claiming a two-shot victory in the Northern Trust Open in Los Angeles on Sunday.
The 42-year-old American fired a final round one-under 70 to hold off England's Luke Donald, who pushed him all the way with a closing 66 at the famous Riviera Country Club.
Mickelson, who was bidding for a hat-trick of wins in the tournament, finished with a two-over 73 to be tied for 45th.
It completes a miserable opening to the season for Mickelson, who was mired in a controversy over his use of a square-grooved Ping Eye-2 wedge going into his title defense.
He decided against using the club and was never a factor as Stricker took charge to take a six-shot lead after completing his third round 66 on Sunday morning.
That lead had been cut to two shots after five holes, but successive birdies on the eighth and ninth saw him regain control.
Stricker, who has won four times since last May to charge up the official world rankings, eventually finished on 16-under 268 with European Ryder Cup star Donald showing a welcome return to form after making a slow recovery from a wrist injury.
Dustin Johnson and JB Holmes shared third place on 271. Johnson carded a 66 and Holmes a 67.
Stricker fnished runner-up to Mickelson at last year's Northern Trust Open to spark a remarkable run of form which sees him assume the number two ranking behind Tiger Woods for the second time in his career.