Charles Howell III and Ollie Schneiderjans posted matching 63s to grab a share of the lead after the opening round of the John Deere Classic.
Howell III fired eight birdies in a flawless display at TPC Deere Run to post his lowest round of the season and set the clubhouse target, which Schneiderjans matched late in the day.
Rory Sabbatini birdied his final three holes to join Zach Johnson and Patrick Rodgers in a share of third at six under, with Bryson DeChambeau part of the group a further stroke back.
Beginning on the back nine, Howell birdied his opening two holes and picked up another shot at the 14th before posting back-to-back gains from the 16th to reach the turn in 31.
Howell drained a 15-footer at the first and added another birdie at the next, with a close-range gain at the seventh seeing the American double his cushion at the top of the leaderboard.
Three birdies over his first five holes saw Schneiderjans close the gap on the lead, before a two-putt gain at the par-five 17th was cancelled out by a stray tee shot and bogey at the next.
Schneiderjans rolled in successive gains from the second and added another at the sixth, with a 10-foot birdie at the eighth and another from a similar distance at the last lifting him to eight under.
Johnson opened with three straight birdies on his way to an opening-round 65, which Sabbatini matched when he holed from 18 feet at the last to close a back-nine 30.
Rodgers also sits on six under after a blemish-free start and Chad Campbell threatened the lead with three straight birdies along the closing stretch, only to go out of bounds and bogey the penultimate hole.
This week’s event is the final tournament in the Open Qualifying series, with one player who finishes in the top-five and not already exempt for Royal Birkdale will book their spot for next week’s major.