The Northern Irishman has only a slim chance of retaining the Race to Dubai money-list title but victory would ensure a spectacular end to a year in which he also won the $10 million FedExCup series in the United States.
"I still have a lot to play for this week," McIlroy told Sky Sports television on Sunday. "If I can win I will finish the year as world number one so that's a huge incentive."
Day has been top of the rankings since March while McIlroy was last number one in August 2015.
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The Northern Irishman is fourth in the European Tour money list behind British Open champion Henrik Stenson, U.S. Masters winner Danny Willett and Swede Alex Noren who landed the Nedbank Challenge crown in South Africa on Sunday.
McIlroy did himself no favours by missing this month's Turkish Airlines Open because of security fears but he stood by his decision.
Asked if he regretted missing the event, he said: "No, not at all. If I hadn't won the FedExCup then maybe it would have been a different scenario but I have won the Race to Dubai before and hopefully I can win it again.
"I think (number one) Henrik is the favourite this year. He is the guy who is playing well and has got the form. I think the course suits him better than Danny, he hits the ball higher which is always an asset round here."
(Reporting by Neil Robinson; Editing by Tony Jimenez)
