MEXICO CITY • Phil Mickelson ended his longest title drought that spanned 101 tournaments at the WGC-Mexico Championship on Sunday to give him hope of adding to his three Green Jackets at the Masters next month.

The five-time Major champion summed up the breakthrough in one word - incredible - after a par putt on the first play-off hole helped him overcome Justin Thomas, the world No. 2 and reigning PGA Tour Player of the Year.

He felt the manner of his victory was vindication for the countless hours he had put in on the greens.

He overcame a two-stroke lead by Thomas with birdies on the 15th and 16th holes in a final round of five-under 66 that included seven birdies and a pair of bogeys.

"I don't know what to say," the Hall of Famer told Golf Channel after his 43rd Tour win, a US$10 million (S$13.2 million) World Golf Championship event.

His last trophy was the 2013 British Open.

"It has been a tough go the last four years. Not playing my best, but to have the belief I was going to get there and finally break through and do it feels incredible.

"It just validates the hard work I've put in and the struggle over the last few years to get my game back."

And with the Masters coming up in a month, the 47-year-old believes he can be a threat again after missing the cut in 2016 and tying for 22nd last year.

"I feel like I'm starting to play my best golf," said the world No. 18, who this week jumped 16 places in the rankings.

"I know how great these young players are. Yet I welcome and cherish the opportunity to compete against them."

His fellow American Thomas, the PGA Championship title-holder, was coming off a victory at the Honda Classic last week.

He made six birdies and holed out from the fairway for an eagle at the 18th for a closing 64 that put him atop the leaderboard on 16-under 268.

Being the earlier finisher, the 24-year-old had to wait for more than half an hour to start the play-off. He hit first and was long on the 17th hole before missing a putt for par.

AGENCE FRANCE-PRESSE, REUTERS