Mikko Ilonen carded a course record 64 at Fota Island Resort to establish a commanding clubhouse lead during the first round of the Irish Open.
The 35 year old from Finland made eight birdies and dropped just the one shot during his seven under par effort, which left him three clear of Italy's former Ryder Cup star Edoardo Molinari and England's Matthew Baldwin.
Having turned in a three under 32 Ilonen bogeyed the first – his tenth – after missing the green with a wedge in hand.
However, five birdies in his last seven holes saw the three-time European Tour winner storm to the top of the leaderboard.
“It was a slow start really,” said Ilonen, who lost a play-off to Sergio Garcia for the Commercial Bank Qatar Masters earlier in the year.
“The first sort of four or five holes I felt like I can't get anything going, but I stayed patient and then the birdies kept coming. In the end I managed to hit a couple of good putts which was nice.”
Molinari has been beset by injury problems since making his Ryder Cup debut alongside brother Francesco at The Celtic Manor resort in 2010, but made six birdies and two bogeys in his round of 67.
Three-time Major winner Padraig Harrington leads the home contingent after a birdie from ten feet at the ninth, his last gave him a two under 69 – the same mark as 2012 Ryder Cup Captain José María Olazábal - but Rory McIlroy struggled to a 74.
The 25 year old McIlroy had the added incentives of being able to move top of The Race to Dubai and getting back inside the top five on the Official World Golf Ranking with a good performance, but could only finish three over par in perfect conditions.
"I still drove the ball great and got in the positions that you need to, but short-sided myself a couple of times, hit a couple of loose shots with my wedges and could not get a putt to drop," said McIlroy, who had carded an approximate 62 in Wednesday's pro-am.
"I was pretty sloppy with the scoring clubs so I might head to the range this afternoon to work on those. I need to do better tomorrow to be here for the weekend."
England's Matt Fitzpatrick, who was the leading amateur in last week's US Open, carded a one over 72 in his first tournament round as a professional.