Lee Westwood has set the pace ahead of a faltering Rory McIlroy as the Race to Dubai reached a critical stage in the season climax Dubai World Championship at Jumeirah.

The Englishman, who was crowned European No1 back in 2000, shot a second-round 66 to take the lead on nine under.

McIlroy, the 20-year-old from Northern Ireland, ought to have set a better target after taming the outward nine of the Greg Norman-designed Earth Course in five-under-par 31. But it all fell apart as he came home in 38 — and only two players all day had shot worse than that.

A 69 left McIlroy on seven under and sharing second place with Ireland's Padraig Harrington, Ross McGowan of England, South African Louis Oosthuizen and Camilo Villegas of Colombia.

Westwood's advantage, while slim, will be vital going into the weekend. As it stands in the money list, he is some £115,000 shy of leader McIlroy.

But a tournament victory on Sunday would give Westwood the money list title no matter where McIlroy finishes.

Not that Westwood's round was perfect. It started well enough with two straight birdies. But he failed to birdie again until hitting his approach to seven feet on the 486-yard 16th and holed out for a three.

At that point he was one shot adrift of Harrington. But the Dubliner had a disastrous finish when he put two balls in the water at the 18th for a double-bogey seven.

Westwood pressed home his advantage with a birdie at the last to stay ahead of McIlroy.

The battle for the money list title is now almost certainly a two-horse race after outside contenders Martin Gaymer of Germany and Londoner Ross Fisher failed to make an impact in their second rounds.

Gaymer, the 24-year-old who missed a vital couple of months after breaking some toes in a karting accident, returned a second successive 71 to stand at two under par.

Fisher followed up his 73 with a 71 to go level, but that still left him in the lower half of the 58-player field. Needing a win or second place on Sunday, his 29th birthday, to have any hope of overhauling his three rivals, it looks as though Fisher is definitely out of it.

At least he had the consolation of knowing some big names were also struggling in the desert heat. Luke Donald and Ian Poulter shot second rounds of 72 and 74 to enter the weekend one over par.

Justin Rose is three over after a 75, while Ernie Els is in second from last place on four over after another 74.

Meanwhile, Welshman Craig Smith claimed the halfway lead at the Johnnie Walker Cambodian Open after carding a six under 66. The 29-year-old is chasing his maiden win on the Asian Tour and put himself in contention with seven birdies — including two on his last two holes — against one bogey to move two shots clear of the rest of the field with a two-day total of nine under 135.

Overnight leader David Gleeson of Australia dropped into a group of six players tied for fifth after carding a 71 at the Phokeethra Country Club and moved three shots behind Smith.

“I managed to hit some good shots to give myself a chance,” said Smith. “I only had one bogey on each day so things seem to be falling in quite easily for me. I hope it continues.”