Lucas Herbert leads Australian Open from Jason Day at halfway

Jason Day defied the afternoon winds to emerge as the hot Australian Open favourite on day two of the tournament.

Day is breathing down the neck of halfway leader Lucas Herbert after wowing fans with four straight birdies on the back nine en route to a second-round three-under-par 68.

The former world No. 1 climbed to eight under for the championship, just one behind Herbert, who capitalised on perfect morning scoring conditions with a sizzling 66.

First-round leader Cameron Davis cooled off with a one-over 72 but remained right in the mix in third spot at seven under.

Australian US PGA Tour players Matt Jones, the 2015 champion, and Cameron Smith, runner-up last year to Jordan Spieth in a playoff, share fourth at four under after respective second rounds of 67 and 69. Former Australian Masters champion Nick Cullen (72) and veteran Richard Green (68) are also at four under and four off the pace.

Spieth, though, faces an uphill battle retaining the Stonehaven Cup after failing to make any inroads on the leaders. His second-round 71 leaves the world No. 2 and three-time major winner eight shots adrift of Herbert.

While Day is undoubtedly in the box seat heading into the weekend, Herbert, who famously slept in the Carnarvon Golf Club car park during Open qualifying three years ago then led after the first round last year at Royal Sydney, collected six birdies before dropping his only shot of the day at the last.

Having sharpened his shorter game this year, Herbert believes lessons from last year's Open, where he faded to finish tied 20th, will be a big help when he duels with Day in the final group on Saturday.

"I think more mentally than anything because, by Sunday afternoon, I was wrecked," Herbert said of how he was better prepared to go on with the job this time around. "It takes so much out of you to be [around the lead]. I learnt a lot from that. I don't need to waste a lot of energy thinking about it."

Herbert, 21, offers a feel-good story as a grafting home-tour pro coming good.

A $Aus40,000 cheque for finishing second in last week's NSW Open -- at 18 under par -- got his finances for the year out of the red, but the former amateur star admits the life and challenges of an average young tour pro came as a rude shock.

"As an amateur you stand on the first tee and you could hit it in a five-yard slot. Then you stand up there as a pro and it's for your living. "You're like 'please hit the ball, please make contact and don't be a YouTube hit'.

"For most guys, [another big challenge is] working out who is in your team and who's there for the right reasons, especially friends. I will look at my phone in 10 minutes' time and there will be 50 messages and 45 are from people you don't hear from until you start playing well and they see you on TV. Find the guys who message you when you finish fourth last in a tournament and just want to go out and drink every single beverage in the vicinity of the town you are in.

"Leaving the amateur ranks you see guys like [ex amateur stars] Curtis Luck and Ryan Ruffels getting invites on tour, flying in private jets everywhere, staying in five-star hotels and you think that's what you are going to get and then you turn pro and you are so horribly mistaken. You are like, 'I am playing a pro-am for how much again?"