Phil Mickelson held off a strong challenge from playing partner Jeff Quinney to win the Northern Trust Open by two shots at Riviera Country Club on Sunday.

The world number two, who squandered an early three-stroke cushion to trail by one after the turn, recovered to clinch his 33rd PGA Tour title, and 16th on the West Coast, with a one-under-par 70.

Mickelson, beaten by fellow American Charles Howell III in a playoff at Riviera last year, piled up three birdies and two bogeys in sun-soaked conditions for a 12-under total of 272.

Quinney, a stroke behind Mickelson overnight, had to settle for second place after rolling in a 25-footer to birdie the last for a 71.

Britain's Luke Donald birdied the final two holes for a 68 to share third place at seven under with British Open champion Padraig Harrington (68).

"This is pretty cool," a beaming Mickelson told reporters after triumphing for the first time at Riviera in 10 starts.

"I have wanted to win this for such a long time. It was a tough fight today because Jeff played so well. He gave a few (shots) back at the end but it was a good battle.

"Last year was really the first year I played well here and to break through with a victory feels terrific," added the San Diego native who first played at Riviera as a 17-year-old amateur.

Mickelson appeared likely to run away with the tournament when he doubled his overnight lead with a birdie at the par-five first after reaching the green in two and two-putting.

Quinney bogeyed the third after missing the green to the left with his approach to slip three strokes off the pace.

The 2000 U.S. amateur champion rallied with birdies at the par-three sixth, where he hit his tee shot to three feet, and the par-four eighth, where he rolled in a 16-footer.

Quinney benefited from a two-shot swing at the par-four ninth, where he coolly sank a birdie putt from 11 feet, to claim the outright lead for the first time.

Mickelson bogeyed the hole after pushing his second shot well right of the green into the rough beyond the cart path and failing to get up and down to save par.

However, the momentum shifted back in Mickelson's favour after the turn.

"I knew that I needed to play a good back nine," the left-hander said. "The fact that he and I were separated (from the field) and that other guys weren't really close to catching us, it was just a head-to-head, nine-hole battle.

Mickelson birdied 10 and 11 to regain a share of the lead with Quinney, who stayed level by sinking a 21-foot birdie putt on the 11th green.

Quinney's bold bid for a maiden PGA Tour victory unravelled with four bogeys in five holes from the 13th where he three-putted from long range.

He lipped out from seven feet on 14, dropped on 15 after failing to find the green and missed a three-footer on 17 to give Mickelson a three-shot cushion.

Reuters.