Jason Day was left shaking his head after his sensational scoring streak ran dry just when a US PGA Tour victory was in his sights in Las Vegas.

Well back at the halfway mark, the Australian caught fire with a run of 17 birdies in 24 holes amid closing rounds of 64 and 65.

By the time he'd covered the front nine at TPC Summerlin in seven-under yesterday, the 25-year-old Queenslander was in third place and just two shots from the lead.

But he could only manage one further birdie on the 16th and finally stumbled with a double bogey on the last to finish fourth, six shots behind winner Ryan Moore.

American Moore shot a 66 to win by one from Zimbabwe's Brendon de Jonge (67) at 24-under 260 with Sweden's Jonas Blixt (70) third at 20-under.

Day was at a loss to explain why his hot streak ended midway through the final round.

''I don't know, I hit a lot of good quality shots on the back nine, the front nine it just seemed like I had a perfect number every time into the greens,'' he said. ''The back nine it just felt like I was a little bit in between clubs. But other than that I hit it great all day, I can't be disappointed … This was my 16th event [of the year] so I haven't really played that much.'' AAP