American Jordan Spieth is outright leader after firing a four-under 67 at The Australian on Thursday as Scott signed for a three-over 74, salvaging his round after a horror show on the front nine.

He racked up a double bogey on the first – the trigger for an uncharacteristic five-over outwards nine – as his putter went cold in the improving afternoon conditions.

A bogey-free back nine at least helped him to begin clawing back the enormous ground he conceded early, least of all to world No.1 Rory McIlroy after his measured two-under 69 in the morning session.

Frustrated with his early mission to correct last year's late Australian Open fadeout, Scott went straight back to work after lodging his scorecard. He is balancing the projected cut highwire with only the top 60 making the weekend's action.

"It's a bad start," Scott said. "I made the worst of my worst shots and didn't convert any of the good ones early and then played good on the back [nine]. I'm on the back foot again this week.

"I've got to play three really great days now and it seems like what I'm doing week after week. I can claw my way back into it [Friday] morning, claw my way into red figures and hopefully I won't be too far back coming into the weekend."

To sum up Scott's struggles, the former world No.1 hasn't missed a cut on the US PGA Tour since the Byron Nelson Championship in May 2012. Spieth, this year's US Masters runner-up, had no such problems and was left to rue a dropped shot on the 17th which halted his charge late on the opening day. He finished seven shots clear of the man he has used as a role model on and off the course – and a shot ahead of Australians Aron Price and Scott Gardiner, whose seven iron landed a hole-in-one and a Lexus on the 11th.

Spieth strung together three straight birdies on the back nine before his late blip, but warned the conditions were only going to get harder over the weekend.

"I think it was scoreable for us and I think we got really, really lucky with the [afternoon] draw," he said. "It's a challenging golf course. There's trouble around every turn if you're not hitting it in the right spots."

McIlroy's Australian Open title defence begun in a steady fashion, finishing with a two under 69 in the first round, tied for fourth. McIlroy hit four birdies and two bogeys in an up-and-down morning in wet conditions.

It was a similar slow start to last year's campaign, when the Northern Irishman stormed home to lift the trophy with a one-shot victory over Scott at Royal Sydney, despite trailing the Australian by seven shots after the first round.

McIlroy insists there are plenty of opportunities to post better scores in the coming days.

"Yeah, I definitely feel like there's a better score out there," McIlroy said. "I gave myself a lot of chances early on in the round and didn't really take them. I started off the round, I hit the ball well and then in the middle of the round I hit a few loose shots, a few scrappy shots and I created a couple of good up-and-downs for pars."

McIlroy will tee off for his second round on Friday afternoon, providing him with the chance to recover from jet lag after arriving in Australia from Dubai on Monday night. "It has been a long season, there's a lot of travel involved but I guess a little bit of jet lag but I'll just try and get over it as best I can. It was an early wake-up call this morning, so try and get as much rest as I can between now and starting off again [on Friday]."