Johnson storms six shots clear in Shanghai's World Golf Championships

Brooks Koepka made a promising start to his third round, but fell away to leave Dustin Johnson with one hand on the title.

World number one Dustin Johnson looks well set to clinch the World Golf Championships, after extending his lead on Saturday.

Dustin Johnson will take a commanding six-shot lead into the final round of the WGC-HSBC Champions after Brooks Koepka's challenge faded in Shanghai on Saturday.

Johnson started moving day with a one-shot advantage over fellow-American Koepka after carding a sublime 63 on Friday and he followed that up with a four-under 68 to go 17 under.

The world number one recovered from a bogey at the first to reel off four birdies on the front nine before losing his way with a double-bogey at the 10th.

Another three gains on the back nine enabled Johnson to have a fifth title of the year firmly in his sights as compatriot Koepka failed to build on a promising start to his third round.

READ: World No.1 Johnson surges to Shanghai lead

The U.S. Open champion led by two shots after stating his intent with birdies at the first three holes, but a triple-bogey took the wind out of his sails.

Koepka fired a wild tee shot left into the trees and was drawn to the foliage again with a poor approach at a horror eighth hole, going on to drop another three shots on the back nine and make only two birdies to sign for a one-over 73.

Henrik Stenson moved up to third with a three-under 69, dropping just the one shot at eight to deny himself a share of second spot with Koepka.

Brian Harman and Justin Rose are a further stroke back following third rounds of 70 and 72 respectively.

Patrick Reed had a day he will want to forget in a hurry, plummeting down the leaderboard following a 10-over 82 which included a triple-bogey and four double-bogeys.