Troy Matteson shot a career best-equalling round of 61 to take a three-stroke lead following the opening round of the John Deere Classic.
Matteson is currently atop the pile on 10-under after the first 18 holes in Illinois, although the American could have been further ahead had he not missed a chance to break 60 with an eagle attempt at the last.
Instead of finding the green Matteson found a bunker but was still able to rescue par, leaving him at 10/1 to win the tournament outright with bet365
"I made a couple of putts that were really, really difficult, and I had a bunch of other really, really good looks," he said.
"Any time you do that and your putting starts to come around you're going to make putts.
"I didn't think it was going to be 10-under, but definitely thought it was going to be good."
Ricky Barnes leads the chasing pack on seven under, while Steve Stricker is a further shot back as he goes in search of a fourth straight John Deere Classic.
Stricker, who is 7/2 to win the tournament, is looking to match the feats achieved by Young Tom Morris, Walter Hagen, Gene Sarazen and Tiger Woods by winning a competition four years successively.
The defending champion shot a six-under 65 to leave himself four shots off top spot in a tie for third, alongside KJ Choi, Robert Garrigus and England's Gary Christian.