MIAMI – Phil Mickelson won the WGC-CA Championship by a shot from fellow American Nick Watney on Sunday, battling dehydration as well as nerves to triumph at Doral.

In a head-to-head duel between the two overnight leaders, Watney paid the price for bogeys on 11 and 12 which followed his eagle on the par-five tenth.

Mickelson's three-under round of 69 allowed him to finish the tournament on 19-under overall and claim his second tour win of the year and his first at a World Golf Championship event.

The left-hander had to receive a drip at a clinic after Saturday's third round due to dehydration and Mickelson said he had been far from well.

"I haven't eaten much in three days, so I really wasn't able to appreciated what others were doing but Nick played some great shots and I was very relieved to come out on top," Mickelson told reporters.

It was an enthralling battle between the two Americans who broke free of the rest of the leaderboard early on.

Once Mickelson had his nose in front, Watney was unable to pull back the shot as both players made par on each of the last six holes.

The 27-year-old Watney, who had made just one bogey all week before his three on Sunday, had an outside chance at birdie on the last but his 29 foot putt fell just inches short.

Watney covered his face with his hat as he realized his slight chance of glory had passed and he was visibly upset with the outcome.

"It definitely hurts, second feels the worst," he said.

"But it was a great week, enjoyed playing against Phil who was not feeling well but played great so hats off to him.

"It kind of sucks for me to play well all week and get beat, but that's the nature of the game I guess and I will be back," added Watney.

World number one Tiger Woods, in his first strokeplay event since his eight month layoff following his knee injury, finished on 11 under-par after his 68 on Sunday, enough to tie for ninth.

American Jim Furyk finished third after a fine back-nine took him to three shots of Mickelson.

Indian Jeev Milkha Singh competed an excellent and consistent week with a 70 which ensured a fourth place on 14 under.