Defending champion Zach Johnson set the pace again after the opening round of the John Deere Classic in Illinois.
Johnson went around Deere Run in a seven-under 64 to sit atop the leaderboard alongside Colombia's Camilo Villegas.
Americans Matt Bettencourt and Daniel Summerhays and Zimbabwe's Brendon de Jonge were a stroke further back.
Johnson is searching for his first PGA Tour win since his success 12 months ago and quickly returned to the form that earned him last year's title.
The 37-year-old shot a flawless round of seven birdies with his playing partners Steve Stricker, who won this event three years running before Johnson's win 12 months ago, and Davis Love III both carding a four-under 67s.
Love's round ensured he remained in contention to continue his record of having played in 26 consecutive Open Championships since his debut in 1987.
The 49-year-old will not, however, play at Muirfield next week unless he wins in Illinois.
Overcoming Johnson and Villegas will pose a major hurdle though.
Villegas was impressive as he blotted his round only with a bogey on the par-four ninth.
The 31-year-old, without a Tour win in over three years, recovered purposefully with birdies on four of his next five holes to shoot up the standings.
Johnson's round continued his fondness with a course that he has now shot 72 under on in total since 2009.