Eight birdies put Sweden's Joel Sjoholm one stroke clear with a round of 64 in the opening round of the BMW Italian Open.
The 27-year-old had eight birdies in his flawless round at Royal Park I Roveri as defending champion Robert Rock could only shoot two under.
Italian Francesco Molinari was the best placed of the Ryder Cup-bound trio in the field as he shot four under, with Germany's Martin Kaymer carding two under and Belgium's Nicolas Colsaerts firing a one under 71.
Sjoholm, who was born in Chile but adopted as a baby and took up the game at the age of three, did not drop a shot as he finished one ahead of England's Lee Slattery who moved to seven under in one of the final rounds to be completed.
Two of Slattery's seven birdies came on the final two holes to put him one stroke ahead of a group of seven.
A late charge by David Howell had seen him join Richard McEvoy and Richard Bland, South Africans Keith Horne and Garth Mulroy, France's Victor Dubuisson and Northern Ireland's Gareth Maybin on six under.
Despite his score, Sjoholm felt he had not necessarily produced his best golf.
"It's more fun now I've finished," he said.
"I hit it basically everywhere. I was in the woods a lot and made some funny birdies today.
"It was a big, fighting 64 rather than a solid 64, but it's great fun to be eight under.
"I want revenge because the last two weeks I actually played quite good golf. Normally when I score well, I have to putt well.
"The last few weeks I've putted quite poorly and missed the cut by one stroke. Both times I felt like I had a good chance to make the cut, but you have to forget and keep moving on."
Molinari's brother Edoardo made his return after three months out following wrist surgery and scored two under with fives birdies and three bogeys in his native Turin.
He said: "The wrist is feeling good. I'm very happy with it. There is absolutely no pain at all.
"It's an okay start. I was very rusty. I hit the ball quite poorly to be honest, but it's more than two months since I last played in competition. It's going to be a long way back to the top but I'll get there."