But Canberra golfer Matt Millar is relishing every moment he spends mixing it with the world's best as he looks to finish with a bang in the final round.

Millar shot two-over par to finish round three tied for 44^th at the world golf championship event at Shanghai's Sheshan Golf Club on Saturday.

It is a far cry from where he sat just days ago as a a surprise round-one leader when he fired three birdies in his first four holes.

Millar had initally managed to hang around the top 20 as the afternoon stars, including Adam Scott, Rory McIlroy and Danny Willett mounted their charge towards the top of the field.

It meant they left the underdog behind in search of his share of the $14.94 million prizepool.

Millar has been struggling to overcome a back injury and was unsure if he would even be able to jump on a flight to tackle the best on the globe less than a week ago.

But the move has paid off, even if he does fall short of the top spots on the leaderboard.

McIlroy earned a one-stroke lead over Louis Oosthuizen as the cream rose to the top in the third round at the WGC-HSBC Champions in Shanghai on Saturday.

McIlroy put on a driving clinic for most of the day, his accuracy and prodigious length off the tee an impressive sight at Sheshan International.

The Northern Irishman carded a bogey-free five-under-par 67 that could have been considerably better had his putter been hotter, but his performance nevertheless was enough to move within striking distance of his fourth victory of the year.

A precise wedge for a tap-in birdie at the par-five 18th allowed McIlroy to inch ahead of Oosthuizen at 15-under 201.

South African Oosthuizen threw down the gauntlet with birdies at the first five holes en route to a 65, the day's best score in ideal conditions.

And American defending champion Xander Schauffele made his presence felt, birdies at the final three holes lifting him within two shots of the lead.

Halfway leader Matthew Fitzpatrick was also two behind after battling to a 70.

Home favourite Li Haotong gave his large gallery plenty to cheer about early with five birdies in the first six holes in a bold quest to challenge for the first Chinese victory at a World Golf Championships event.

But the party did not last as he came undone with an error-strewn stretch that included triple-bogey at the par-four 13th, where he knifed a bunker shot over the green into a hazard.

He shot 74 and fell nine shots behind the pace on a frustrating day which ultimately left his hopes of securing the title in tatters.