Brooks Koepka, newly established on top of golf's world rankings, talks to media in Shanghai today ©Getty Images

Brooks Koepka, newly established as golf's men's world number one in a season where he has won two majors, faces a stern test of his credentials as part of a stellar field at the World Golf Championships event that starts in Shanghai tomorrow.

The 28-year-old American, who this year became the first man since 1989 to successfully defend the US Open title and who added a victory at the PGA Championship, capped the best year of his career by reaching the top of the world rankings for the first time with a victory at the CJ Cup in South Korea last weekend.

Such is his form that few would bet against him winning this annual tournament at the Sheshan International Golf Course this week, but to do so he will have to beat another four of the world's six best golfers.

"I'm looking forward to teeing it up as number one," he told reporters today.

"I think that's something every golfer kind of dreams of and every golfer wants to accomplish.

"I'm looking to build on that lead, grow it, and that way I can be number one for a while.

"The goal isn't just to get here, it's to stay here."

All three of the 2018 major winners, 10 of the victorious European Ryder Cup team and five previous champions are also competing at the final World Golf Championship tournament of the year.

Defending champion Justin Rose of England poses for a photo during the pro-am prior to the event at Sheshan International Golf Club ©Getty Images
Defending champion Justin Rose of England poses for a photo during the pro-am prior to the event at Sheshan International Golf Club ©Getty Images

While Englishman Justin Rose, the Olympic champion, is in two of those categories after coming back from eight shots down over the final round to lift the trophy last year, his Ryder Cup team-mate Rory McIlroy has never won the event.

The Northern Irishman, who has had five top 10 finishes, has not played since Europe's triumph in Paris and needs a good result to start cutting into Open champion Francesco Molinari's lead at the top of the European Tour's Race to Dubai.

"I feel like I need one win, maybe two out of the next three, to have any sort of a chance," McIlroy, a four-time major winner, said.

"I'm playing with Francesco the first couple of days, so it's good to keep an eye on him, I guess.

"I need to play some very, very good golf over these next few weeks to at least have a chance."

Dustin Johnson has plenty to prove as he seeks to set up his 2019 PGA Tour season in the exclusive field in central China.

Not only was it his lead that Rose overhauled to win the title last year but it was the 34-year-old American who made way when his good friend Koepka became world number one last week.

Johnson plays in the final group with McIlroy and Molinari.