Denny McCarthy was pleased with his all-round game as he opened up a one-shot lead after the first round of the AT&T Byron Nelson in Texas.
The 26-year-old American fired an impressive eight-under-par 63, despite an early double bogey, while Brooks Koepka carded a 65.
McCarthy was still two-over after five holes at Trinity Forest but then enjoyed an incredible sequence of 10 birdies in his next 12 holes as he surged up the leaderboard.
Tyler Duncan and Tom Hoge posted 64s while Koepka is in a nine-way tie for fourth on six-under.
Japan’s Hideki Matsuyama shot a 67 while local star Jordan Spieth, a member at the course, came in with a 68.
Jonas Blixt fired a 65 with his fellow Swede and former Open champion Henrik Stenson posting a 67.
McCarthy said afterwards: “The conditions were soft. I’m not the biggest hitter so the golf course played somewhat long for me but I really put some work in on my mid-irons and long irons so that gave me a chance to work on those today.
“I hit a lot of great ones today and I’ve been putting great in the last couple of months so I kind of matched up the ball-striking with the putting.”
McCarthy turned professional after playing in the 2015 Walker Cup while his best performance in a major came in the US Open four years ago when he finished in a tie for 42nd.
McCarthy is available at 26.00 to win the AT&T Byron Nelson, while Koepka can be backed at 6.00.