Experienced Briton Lee Westwood led the field with an opening 66 but Open champion Henrik Stenson, who leads the money-list, shot level-par 72 and his Swedish compatriot Alex Noren and Britain's US Masters winner Danny Willett had rounds of 71.
World number two McIlroy, fourth on the money list, needs victory in Dubai to win the race with Stenson finishing outside the top 45, Willett failing to make the first five and Noren the top two.
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But the Northern Irishman had problems on the greens and made a double bogey and four bogeys to slump to a tie for 55th place in the 60-man field.
Frenchman Julien Quesne and Belgian Nicolas Colsaerts were tied for second behind Westwood after rounds of 67, one shot ahead of Spain's Sergio Garcia, Italian Francesco Molinari and Dutchman Joost Luiten.
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