The Irish trio of Michael Hoey, Cormac Sharvin and Robin Dawson endured difficult opening rounds at the Australian PGA Championship on the Gold Coast as Jake McLeod set the pace on Thursday.
McLeod continued his strong home season with a six-under-par 66 to take a share of the lead alongside compatriot Matt Jager.
Hoey and Sharvin struggled to a six-over round of 78, which was two better than Dawson, whose seven bogeys and double bogey will see him likely to miss the cut.
Queenslander McLeod, who claimed his maiden professional title at the New South Wales Open earlier this month, rolled in six birdies in a bogey-free round to upstage a slew of bigger names at the European Tour co-sanctioned event.
He and Western Australian Jager ended the day one stroke ahead of South Korea's Eom Jae-woong and Dimitrios Papadatos, who came second at the Australian Open two weeks ago, at the Royal Pines Resort.
Australian number two Marc Leishman was a stroke further adrift on four-under in a group five players that also featured Spain's Adrian Otaegui.
McLeod finished third at the Australian Open at The Lakes course in Sydney and the 24-year-old credited his recent good form to the help of a new psychologist.
"I just need to stay really focused on the shot and have a bit of a laugh out there and just stay relaxed," said McLeod, who got off to a flying start with four birdies in six holes after teeing off from the 10th.
Jager also started brightly in brilliant sunshine from the 10th, grabbing eagles at the par-five 12th and 15th holes to make the turn at four-under before adding three birdies and a lone bogey to close out his round.
John Senden, twice a winner on the U.S. PGA Tour, was left fuming with officials at the ninth when his driver's shaft snapped mid-swing at the tee and pinched his hand.
Although the big-hitting Australian had not made contact with the ball, it was ruled a stroke. Lacking another driver in his bag, the 47-year-old removed the tee and hit his second shot with an iron before going on to bogey the hole.
Senden finished with an even-par 72, one better than playing partner Geoff Ogilvy, the 2006 U.S. Open winner.
Defending champion Cameron Smith, who won last year's tournament in a playoff, opened with a 70 to be four off the pace on two-under, in a huge group that included Briton Andrew Johnston.