SHANGHAI (AFP) - World No. 1 Dustin Johnson imploded as Justin Rose stormed back from eight shots behind overnight to win the US$9.75 million (S$13.3 million) WGC-HSBC Champions by two strokes in a thrilling finale in Shanghai on Sunday (Oct 29).

Englishman Rose, who started the concluding day joint fourth, fired a final-round 67 to finish 14-under par 274 and emerged victorious from a nail-biting four-way fight that also included Henrik Stenson and Brooks Koepka.

The trio all finished tied in second.

Johnson was chasing a sixth prestigious World Golf Championship (WGC) title and looked to have put himself out of sight on Saturday evening with a handsome six-shot lead on fellow American Koepka.

But on another blustery day, this time accompanied by smog and cooler temperatures, Johnson started with two bogeys to immediately give the chasing pack hope on the par-72 course.

Johnson, who triumphed at the Sheshan Golf Club in 2013, failed to get his putter going all day and was meticulously pegged back by a combination of Rose, Stenson and Koepka.

There was a moment of levity when a black swan invaded the course.

But the heat was really on the 33-year-old when he carded another bogey at the par-three 12th and Stenson made birdie.

Johnson's good friend Koepka and last year's runner-up Stenson were now a scarcely believable two shots behind.

With the skies becoming gloomier, Johnson was crawling to the finish line.

Rose, the 2016 Olympic champion, was playing in the group ahead and sunk birdies at 11, 13 and 14 to join Koepka and Stenson in hunting down Johnson.

Reigning US Open champion Koepka whittled Johnson's once-healthy lead down to a wafer-thin one shot with a birdie at the par-five 14th.

Another birdie chance went begging for Johnson at the 15th, but at least he was able to smile about it.

But it was not for long as Rose made a seventh birdie at the 16th to draw level in the lead.

Johnson's horror day unravelled further when he found the bunker with his tee shot at the par-four 16th.

His pursuers sensed blood when he carded bogey and Rose and Stenson catapulted over him into the joint lead with two holes to play.

Rose made another birdie at the 17th and made his way to the final hole one shot ahead of Stenson, with Johnson having tumbled to third and Koepka fourth.

Rose signed off with par at the 18th and then faced an anxious wait for the other three to finish.