Rory McIlroy exceeded his expectations with an opening 68 in the WGC HSBC Champions but still saw two of his Race to Dubai rivals ahead of him on the leaderboard in Shanghai.

McIlroy revealed he had lost 10lb due to a severe bout of food poisoning after carding six birdies and a double bogey at Sheshan International to finish five shots behind South Africa's Branden Grace.

Grace is more than 1.1million points behind McIlroy on the Race to Dubai, but each event in the Final Series offers 1.3million point to the winner and the 27-year-old is in a rich vein of form after compiling a perfect 5-0 record in the Presidents Cup in South Korea last month.

A flawless nine-under 63 gave Grace a one-shot lead over Thorbjorn Olesen, Kevin Kisner and Steven Bowditch, with England's Danny Willett - who is second on the money list - another shot back. Scotsman Russell Knox tucked himself into a share of ninth with a 67 while world number two Jordan Spieth, who can reclaim top spot from the absent Jason Day with a top-10 finish, matched McIlroy's 68 to finish alongside defending champion Bubba Watson.

McIlroy was taken ill on Tuesday and missed the following day's pre-tournament pro-am, but could call on the experience of his four previous appearances in the event which have yielded four top-six finishes and a combined score of 52 under par.

"(It was) probably a little better than I was expecting out there to be honest," he said.

"When I was hitting balls this morning on the range I had not been out of bed for basically 48 hours, so I was really stiff. I needed to loosen up quite a lot, but when I got out there I felt pretty good.”

At the Challenge Tour Grand Final in Oman, Peter Whiteford surged up the field with a 67 but still faces a huge task to earn his European Tour card.

The Fifer would need to win this week to break into promotion zone of the top-15 on the money list and his four-under halfway aggregate of 140 still left him seven shots off the lead held by Joachim Hansen.

Scott Henry also sits on the 140 mark while George Murray is a shot further back in a share of 17th. Andrew McArthur (146) and Jamie McLeary (149) still have plenty of work to do to ensure they remain in the card-winning places of the top-15.