Rory McIlroy shot a three-under-par 69 to take a two-stroke lead after the second round of the Shanghai Masters Invitational golf tournament on Friday.
McIlroy struggled with the front nine, bogeying the fourth hole before conceding a double bogey on the difficult, par-four ninth to drop back into a four-way share of the lead.
He recovered with four birdies on the back nine to finish on 11 under.
Ian Poulter is six under after a 71 and Lee Westwood five under following a 70.
US Open champion McIlroy is two strokes ahead of South Korea's Noh Seung-yul.
Noh, 20, made the biggest move of the day, sinking nine birdies for a 63, the lowest round of the tournament so far.
His excellent round saw him move from joint 18th place after round one to second.
McIlroy also led the tournament after the opening round after shooting a bogey-free round of 64.
Noh, ranked 95th in the world, achieved his biggest victory to date at the Malaysian Open last year, where he become the second-youngest winner in European Tour history.
He is also a former Asian Tour rookie of the year.
Anthony Kim of the United States (68) and Louis Oosthuizen of South Africa (66) are a stroke behind Noh at eight under, followed by Padraig Harrington of Ireland (70) and Hunter Mahan of the United States (72).
Mahan, who was in second place after the opening round, also had trouble on the front nine on Friday, bogeying twice and holing just one birdie.
He was at one under for the day until bogeying the 18th hole to finish at even par.
Poulter and Robert Karlsson (69) are six under, and John Daly followed his opening 69 with a 70 to match Westwood, Colin Montgomerie (69) and Masters champion Charl Schwartzel (69) at five under.
There are 30 players, including 10 major winners, vying for the $2 million first prize, the richest in golf.
The International Management Group-run event, being held for the first year, is not sanctioned by a major tour and does not have world-ranking points.