Watson was two shots clear with three holes to play at Sheshan International only to bogey the 16th and run up a double bogey on the 17th after failing to escape a greenside bunker at the first attempt. That dropped the Masters champion one shot behind playing partners Clark and Rickie Fowler, as well as the final group of Graeme McDowell, Hiroshi Iwata and Martin Kaymer.
Clark looked in pole position when he hit his third shot to the par-five 18th to four feet and saw Fowler find the water and Watson a greenside bunker.
However, Watson then amazingly holed his bunker shot for an eagle and Clark’s birdie was only good enough to leave the pair tied on 11 under, with the final group needing to birdie the last to join the play-off.
Kaymer’s chances disappeared when his approach flew over the green into the water, while McDowell and Iwata missed from 18 and 12 feet respectively.
Clark and Watson returned to the 18th for the play-off and Watson found the same greenside bunker with his second shot after Clarke had hit his third to around 20 feet. Watson was unable to repeat his heroics from the sand but after Clark had left his birdie attempt short, the left-hander holed his birdie putt to seal victory.
“For me this is the big one,” Watson said after his third win in 2014. “It’s very big because I always wanted to win outside the US. It’s my seventh win, gets me closer to 10 wins which has always been my goal.”
Speaking about the 72nd hole, the 36-year-old added: “It was such a tough bunker shot you are not really thinking about making it, but I told my caddie it’s been a wild day, a wild couple of holes, but if we can make this it changes everything and it went in like a putt.
“In the play-off, it was funny because the bunker shot I holed was on the same line (as the putt) so we knew the line, we knew it was fast. I was trying to two-putt and it just fell in.”