Mahan was the only player in the field not to card a bogey over the final 36 holes as he finished 16-under-par following a six-under 65 on Sunday.

Fowler, playing just his sixth PGA Tour event, was just inches away from forcing a play-off when he rolled a 20-foot putt past the hole on the 18th green.

The 21-year-old will, though, likely reflect on a missed opportunity on the par-five 15th when, after driving to within range of the green, he opted only to lay-up and then managed just a par.

South Korea’s Yang Yong-eun was third after he carded a 65 to finished 13 under.

Overnight leader Brandt Snedeker endured a terrible final round as he returned a seven-over-par 78, including double bogeys at each of the final two holes, to finish in a tie for 43rd.

Spaniard Alvaro Quiros was the best placed of the European raiders as the Ryder Cup hopeful recovered from double bogeys at the opening two holes to card a 70 and finish six shots behind the leaders.

Ian Poulter, who won at last week’s WGC-Accenture Match Play, was a stroke further back after also posting a final-round 70.

For Mahan it was his first PGA Tour victory since winning the Travelers Championship in a play-off in 2007 and admitted his consistency over the weekend had been the key to his success.

“I played great. Tee-to-green it was flawless,” he said in an interview on Sky Sports 2.

“I put the ball where I needed to put the ball. I gave myself a lot of easy looks, I really didn’t struggled too much with par putts.

“It’s been an ugly west coast for me. I haven’t played as well as I would have hoped so to get a win feels awesome.”

Mahan is also gunning to earn his place on the USA’s Ryder Cup team at Celtic Manor in October after having been a captain’s pick two years ago.

“This a Ryder Cup year so this is a year you really want to play well,” he admitted.

“I defiantly want to make the team on my own.”