Rory McIlroy seized on a series of unexpected errors by Luke Donald and reignited his bid for the European Tour number one title on Thursday.
After the first nine holes of the Dubai World Championship the 22-year-old US Open champion, needing to win to have any chance, was three behind Donald and seven shots off the lead.
But the picture then changed completely on the inward half. McIlroy grabbed six birdies for a 66 that leaves him in third place, only two behind Swede Peter Hanson and one back of Scot Paul Lawrie, while Donald had three successive bogeys from the 14th and signed for a level-par 72.
Should the Northern Irishman lift the tournament trophy on Sunday, Donald will have to finish in the top nine to complete his unprecedented money list double. He finished the day in a tie for 26th.
It did not look the likely outcome when McIlroy lost a ball on only his fifth shot of the day and ran up a double bogey seven, but Donald was in the bushes on both the 14th and 15th and then failed to save par from a fairway bunker at the next.
Hanson, meanwhile, equalled the course record set by Lee Westwood in winning the inaugural event two years ago and matched by Ross Fisher last November.
Hanson's birdie at the short 17th and closing par five denied Lawrie a share of the lead after he had produced six birdies in seven holes from the fifth and then another at the long 14th.
Sergio Garcia, chasing a third successive European Tour win, is fourth after a 67.
Westwood managed a one over 73, which included a double bogey on the short 13th after he had to play his second shot left-handed from the side of a bunker.
The field, already without Justin Rose and Fredrik Jacobson, is down to 57 after Korean YE Yang quit after four holes because of neck and shoulder trouble.