The victor in that match-up will likely take over the mantle of the world's No. 1 golfer when rankings come out Monday.
McIlroy, the top seed in the Gary Player bracket, bested 11th-seeded Sang Moon Bae, 3 & 2 Saturday.
Meanwhile, Westwood -- the No. 1 seed in the Sam Snead bracket -- posted a 4 & 2 victory over Martin Laird.
A pair of Americans will compete against each in the other semifinal battle after each registered a victory in the quarters.
The championship round will follow the Sunday morning semifinals.