With new Open Champion Darren Clarke and three-time Major winner Padraig Harrington among the later starters - Clarke bogeyed the first hole - and last year's US Open Champion Graeme McDowell managing only a 72, McIlroy had the chance to set a really challenging total.
"At four under through ten things were going along quite nicely," he said, "but I didn't drive it great all day and I played some scrappy golf coming in."
The approach to the 14th was a notable exception to that - "all I was trying to do was get it in the front bunker" he commented on a 130 yard shot to within 20 feet of the flag that he had to move nearly 50 yards right to left.
"My driving caught up with me at the end. I just need to be more decisive on the tees - I was stuck in two minds."
McDowell commented: "It was a funny day. I didn't hit it in the fairway much and didn't make much on the greens and then after birdies at 14 and 15 steadied the ship I was a yard in the gorse on the (par five) next and made bogey.
"It was nothing disastrous I suppose and I'm not out of it by any means."
Clarke remained one over after six, while Harrington bogeyed the short third, but birdied the next to be four behind the six joint leaders - Fisher, Green, Moriarty, Lemke, Hansen and German Marcel Siem, who turned in a best-of-the-day 31.
Irish amateur Paul Cutler was only one worse than that, his round having started with an eagle two after he pitched in from 133 yards.
By coming home in a spectacular six under 30 - he birdied six of the next seven holes after the turn - Swede Christian Nilsson was the new clubhouse leader with a five under par 66.
Clarke and Harrington both stood one under with eight to play.