Patrick Rodgers carded an almost flawless seven-under-par 64 to take a two-shot lead at the John Deere Classic after two rounds.
Rodgers was two strokes off the pace when he teed off on the back nine but the American erased that deficit in Silvis, Illinois on Thursday.
Seeking his first PGA Tour victory, Rodgers holed eight birdies and only dropped one shot at the last to be 13 under at the halfway stage of the tournament.
Bryson DeChambeau is Rodgers' nearest challenger heading into the third round at TPC Deere Run.
DeChambeau rose five positions following his second-round 65, which included eight birdies and two bogeys.
Tied for third are fellow Americans Zach Johnson and Charles Howell III.
Johnson maintained his position thanks to a four-under-par 67, but Howell III dropped down the leaderboard.
Howell opened with a 63 to lead alongside Ollie Schniederjans on Thursday, however he posted a 69 to be three shots off the pace.
Chesson Hadley (64), Chad Campbell (68), Kevin Tway (63) and J.J. Henry (64) are a stroke further back at nine under.
Defending champion Ryan Moore, meanwhile, missed the cut.
Moore followed up his opening-round 74 with a 71 to exit the tournament three over - the cut line at two under.