(CNN) -- Unheralded Korean YE Yang leads the Honda Classic in Miami after 36 holes, carding a five-under-par 65 to lie one stroke ahead of overnight leader Robert Allenby, Will Mackenzie and Jeff Overton.
Yang lies one stroke ahead of his rivals after a second-round 65 in Florida.
World number 460 Yang, a five-time tournament winner in Asia, had started the day on the par-70 PGA National in Palm Beach Gardens two shots behind Australian Allenby in a tie for eighth place.
However, after one birdie over his opening nine holes, the 37-year-old -- who began from the 10th tee -- holed three birdies in succession at the first, second and third before taking the lead with another at the par-three seventh.
Germany's Alex Cejka is the leading European in the clubhouse, in a tie for seventh place on three-under, along with Australian Greg Chalmers, who shot a course record-equalling 64.
Northern Ireland teenager Rory McIlroy continued his great start as a professional in the United States by posting a two-under 68 to lie in a large group of players on two-under for the week.
McIlroy, 19, made his debut in America at last week's WGC-Accenture Match Play in Tucson, Arizona, earning rave reviews Stateside as he reached the quarterfinals.
Defending champion Ernie Els had to scramble to make the cut. The South African was four-over and in need of a birdie at the par-five 18th to reach the weekend -- which he accomplished with a seven-foot putt.
Not so fortunate, though, was world number nine Camilo Villegas whose second-round 74 left the Colombian at seven-over, four shots adrift of the cut.