Having finally reached the summit, Brooks Koepka has no intention of giving up his number one ranking any time soon but his first outing as the man to beat could hardly be tougher with a stellar field gathered for this week's WGC-HSBC Champions.

Koepka, twice a major winner in 2018, capped the best year of his career by clambering to 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 going back-to-back at the Sheshan International Golf Course outside Shanghai 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. I think that's something every golfer kind of dreams of and every golfer wants to accomplish," he told reporters on Wednesday.

"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.

While Englishman Justin Rose 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 $10 million event.

McIlroy, 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 British 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 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 looks to kickstart 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 on Thursday but Koepka should be ready for a verbal volley or two when the compatriots catch up in the clubhouse.

"He's a really good player, and obviously I do okay, too," Johnson said of Koepka on Wednesday.

"It's a great relationship and we push each other to get better. And yes, there is a lot of trash talking," he added with a smile.