Golf has a new world number one

LAKE FOREST, IL - SEPTEMBER 20: Jason Day of Australia hits a drive on the 14th hole during the final round of the BMW Championship at Conway Farms Golf Course on September 20, 2015 in Lake Forest, Il

Jason Day has fulfilled his childhood prophecy and stormed to world No.1 after clinching his fourth win in six starts at the BMW Championship.

Day dominated from his opening round 61 at Conway Farms Golf Club, going wire-to-wire by closing with a two-under-69 to be 22 under for the tournament, six clear of his nearest rival.

Ridiculed and hammered when he voiced his dream as a 19-year-old rookie to become world No.1, Day has finally given his critics a serve of humble pie and looks set to fight with Rory McIlroy and Jordan Spieth at the top for years to come.

"Four out of the last six weeks it's been kind of a dream run for me, it's quite shocking, a delirious Day said after becoming the youngest Australian ever to become no.1.

"I thought I always had it in me, but just to be able to do it and play the way I have and finish the way I have has been a fantastic ride."

Sitting back at world No.9 after missing a playoff at the British Open by a shot in mid July, Day has gone on an absolute tear - winning the Canadian Open, the PGA Championship (his maiden major win), the opening FedEx Cup playoff event at the Barclays and now the third playoff event at the BMW Championship.

He leapfrogs Spieth and McIlroy into top spot and at 27 years, 10 months and eight days smashes Greg Norman's mark of the youngest Australian to be the world's best.

Norman was 31 years, seven months, 14 days old when he was on top for the first of 331 weeks in his career while Adam Scott was 33 when he ruled the golfing world for 11 weeks in 2014.

"The last two days were very, very emotional for me, very hard to sleep at night, knowing that I had the chance to get to no.1," Day admitted.

"It's been very, very difficult for me to try and downplay it because I've really wanted to reach this goal for a very long time.

"But it's good to sit in this chair right now, knowing that what I said back when I was 19 years old, it's taken some time, but it's worked out. Now I'm sitting on top of the world."

Instead of rubbing in the noses of those who bet against him, Day took the high road.

"I'd love to say 'I told you so', but that wouldn't be very nice," he added.

"I would just say it's okay to dream big. It's okay to say what you want to do. That was kind of the fuel that lit the fire for me, especially with the dedication over these last few years because I know that a lot of people were thinking against me on that.

"I'm glad I accomplished it."

American rookie Daniel Berger (69) finished second at 16 under, Scott Piercy (70) was third at 15 under with McIlroy (70), Rickie Fowler (69) and JB Holmes (68) sharing fourth at 14 under.

Day also claimed the Farmers Insurance Open back in February and as such it is by far the most successful season by an Australian since Norman had three US wins and two in Europe in 1986, including the British Open.

Day now heads to the 30-man season ending Tour Championship in top spot on the season long FedEx Cup points list, ensuring a win at East Lake Golf Club will see him claim the US$10 million bonus.

Kiwi Danny Lee will also be at the Tour Championship, sitting in 19th on the FedEx Cup list.

-AAP