The English golfer is looking for his first win of the year, and he started the opening round with three birdies.
The Englishman's long-time bagman Billy Foster has been advised to rest his injured knee, but that did not affect the world 47, who is looking for his first win of the year.
He started the opening round with three birdies on the from World Tour Championship nine, and made another four on the back along with a bogey on the 12th hole.
Julien Quesne of France and Nicolas Colsaerts of Belgium were a stroke behind the inaugural 2009 champion at Dubai's Earth course of Jumeirah Golf Estates.
"Billy normally thinks for me," said Westwood.
"I probably have to do more this week, think a little bit more, which is probably a good thing,? added Westwood when asked about having someone new on his bag.
"Obviously a different caddie doesn't know my game. He's only had one round on the bag. He's sort of making it up as he goes along.
"I have full confidence in him, and his yardages and the way he reads the wind and stuff like that. Put my game to his information."
Spain's Sergio Garcia made a late double bogey, on the par-4 16th hole, to fall to four-under par 68, tied fourth alongside Joost Luiten and Francesco Molinari.
With none of the four players contesting the Race to Dubai crown managing to get a fast start, Sweden's Henrik Stenson remained the favourite despite a poor round of 72 by his standards.
But world No2 McIlroy had an even bigger shocker, recording his first over-par round in the tournament, a three-over 75.
Danny Willett, who needs to finish inside the top-5 to have any chance of beating Stenson to the European No1 honour, shot a one-under par 71, which matched Alex Noren's effort.
Willet and Noren are ranked second and third in the Race to Dubai at the start of the final week of the European Tour season.
Stenson, who made just one birdie and one bogey, said: "You know, the couple of good putts didn't go in, and of course, the bad ones normally don't find the bottom of the cup.
"I stayed out of trouble most of the day but nothing too exciting either to play or to watch. Hopefully, I can turn that around and play a better round tomorrow."
McIlroy, who made three birdies and a double bogey in his last five holes, did not speak to the media. He was whisked away for random dope test following the round.
Westwood meanwhile was delighted with the way he played in tough scoring conditions on a day when only 32 players managed to break par.
"This is as good as I've played for quite some time. I've found a couple of keys in different parts of my game and I've been working on them hard. All came together today."