During a flawless opening round, Westwood, a native of England, five-time Ryder Cup star and 18-time European Tour tournament winner, made five birdies and no bogeys.
Haig, a South African who was a first-time winner at the 2007 Johnnie Walker Classic, has missed the cut in three of his first six starts this season, including two straight.
"My confidence is good, obviously," said Westwood, who finished in a tie for second place at last week's Abu Dhabi Golf Championship. "I can't help but be confident."
There were 58 players overall at even-par or better.
Defending champion Retief Goosen withdrew Wednesday because of an eye injury.