Rory McIlroy two behind leader Jordan Spieth at Australian Open

McIlroy pipped Scott by one shot to win last year's Australian Open

Defending champion Rory McIlroy is two behind American leader Jordan Spieth after hitting an opening two-under-par 69 at the Australian Open in Sydney.

McIlroy carded four birdies and two bogeys as Masters runner-up Spieth took a one-shot lead over Australian duo Aron Price and Scott Gardiner.

"Anything in the 60s was a pretty good score," said world number one McIlroy.

Adam Scott, pipped by Northern Irishman McIlroy in last year's event, opened with a double bogey in a three-over 74.

Spieth, 21, sank six birdies in tricky conditions at the Jack Nicklaus-designed The Australian course.

Adam Scott struggled to an opening 74 in Sydney

"Overall, it was a solid round, I putted great, my short game kept me in," Spieth said.

"My approach for Friday is just trying to keep it consistent, don't worry about the scoreboard and let my putter do the work."

McIlroy, 25, confessed to feeling the effects of jet-lag after flying in from Dubai following his runner-up finish behind Henrik Stenson at the World Tour Championship.

"I started off OK but in the middle of the round I hit a couple of loose shots and actually made a couple of good up-and-downs for pars, but then made three birdies on the back nine against one bogey," he said.

McIlroy overhauled Scott with a birdie at the final hole to win last year's Australian Open at Royal Sydney in what was his only 2013 tournament success.

However, Scott, 34, has work to do to get back into contention this week after his poor start on Thursday.

The former world number one was in trouble from the start with a double-bogey at the first hole on the way to dropping five shots in his opening nine holes.

Japan's Achi Sato joined Spieth in the lead late in the round only to drop back to two under after two bogeys.