Phil Mickelson won a play-off in Mexico City ©Getty Images

Phil Mickelson overcame the longest drought of his professional career to win the World Golf Championship event in Mexico City via a play-off round.

It marked the American's first victory since the 2013 British Open in Muirfield - more than 100 tournaments ago.

The 47-year-old was forced to dig deep at the Club de Golf Chapultepec to win a play-off against fellow countryman Justin Thomas.

Both men had earlier finished on 16-under-par.

"I don't know what to say," Mickelson said afterwards. 

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

Phil Mickelson pictured midway during his final round ©Getty Images
Phil Mickelson pictured midway during his final round ©Getty Images

"I believe that more is to come, and I feel like I'm starting to play some of my best golf. 

"To culminate here in Mexico City with a World Golf Championship victory is exciting to me beyond words because it just validates the hard work I put in and the struggle for the last few years to finally get my game back."

Thomas had holed out from the fairway to take the contest into a play-off, but then bogeyed the 17th hole.

Englishman Tyrell Hatton and Spaniard Rafa Carbera Bello each finished a shot behind at 15-under for a share of third position. 

The tournament is one of the four annual World Golf Championships organised by the International Federation of PGA Tours.

India's 21-year-old newcomer and overnight leader Shubhankar Sharma struggled on the final day and slipped back to 10-under-par.