Jason Day makes his charge at Australian Open

Playing in the afternoon when the wind was at its strongest, Day defied blustery conditions to shoot a second round three-under par 68 and reach the halfway point at eight-under.

That left the Australian just one stroke behind outright leader Lucas Herbert, who made the most of his early tee-off time and carded a 66.

Spieth, still rusty after taking an extended break since the Presidents Cup, battled his way to an even-par 71 to be one-under overall but was still hopeful of catching up to the frontrunners over the weekend.

“On this golf course, more than just about any that we play, I feel like you can make up more ground and come from behind,” he said.

Day, chasing his first victory of 2017 and his maiden win at his national open, briefly joined Herbert in a share of the lead when he drained a 20-foot putt on the 15th hole for his fourth successive birdie.

The former world number one slipped a shot behind when he bogeyed the 17th but scrambled a par on the last after finding a fairway bunker with his drive.

With a seven-stroke advantage over Spieth, Day is now a strong favourite to win the Stonehaven Cup but he said he fully expected the American to claw his way back into contention.

“If he gets something going on the weekend, he can hole a lot of putts and make a lot of birdies and make a charge,” Day said.

“Seven strokes is obviously not enough but I’d like to keep pushing forward and hopefully I don’t see him in my rear view mirror at all.”

Herbert followed up his first day 67 with six birdies to set the pace at nine-under 133 and remain in front.

The recently-turned professional also led the Australian Open last year before eventually finishing 20th, but said he was better equipped to handle the pressure this time.

“I finished pretty high up last year in the Aussie Open (so) I can play well and I’m proving to myself that I can play well in these big events against these big players,” Herbert said.

“I’m feeling like I belong out there, which is the big thing.”

Hoping to capitalise on the benign morning conditions after playing his opening round in gusting winds on Thursday, Spieth only managed two birdies in the second round.

The three-time major winner has not played in six weeks and is missing his regular caddie Michael Greller, who remained at home after the recent birth of his son.

But Spieth said he was making progress.

“It’s just been the short game rust that’s kind of hurt me a bit the last couple of days that prevents me from being five or so under and then instead I’m at one,” he said.

“But the more I’m getting them on course the better, and we’ll go forward and try and shoot a low round.”