All eyes were on the world number one and second-ranked Tiger Woods after they had been paired together for the start of their 2013 seasons, but Woods was not much better - a level-par 72 left him five behind early clubhouse leader Jamie Donaldson.
McIlroy, who on Monday had been unveiled as Woods' Nike stablemate in a mega-million dollar club, said: "I feel I was just a little bit rusty."
The 23-year-old's last outing was his DP World Tour victory in Dubai in late November. In that event he finished with five straight birdies, but it was a different story on his return to action.
At least his girlfriend Caroline Wozniacki put in a much more satisfactory day's work, reaching the third round of the Australian Open tennis tournament with a 6-1 6-4 win over Croatian Donna Vekic in Melbourne while McIlroy was on the course.
"I didn't drive it particularly well and didn't hole any putts," added McIlroy, whose round included double bogeys at the short 12th - his third - and 439-yard third, where he drove out of bounds.
It was Woods who produced the worst shot of the pair, though. After turning in a two-under 34 his drive down the 405-yard first went barely 120 yards, not even reaching the fairway.
"My game plan was three-iron or five-wood and then I changed," he stated afterwards. "I was not committed to the shot - I should have backed off. I had a strategy, I didn't keep to it and paid the price."
He followed it with another bogey at the long second and three-putted the ninth for another, but there were also four birdies on his card compared to McIlroy's two - and it was the ninth time in 12 head-to-head clashes that he had shot lower than the Northern Irishman.
Donaldson, already looking forward to his US Masters debut in April after climbing into the world's top 50 on the back of his Irish Open victory last summer, led by one from Dane Thorbjorn Olesen, also Augusta-bound, and Spaniard Pablo Larrazabal.