Texas local Jordan Spieth and unheralded J.J. Spaun are tied at the top after the opening day of the AT&T Byron Nelson at TPC Craig Ranch in Dallas on Thursday.
Spieth, who dramatically finished with a 55-foot eagle, and Spaun both carded opening rounds of nine-under 63, to lead by one shot ahead of a group of four including Rafa Cabrera Bello, Aaron Wise, Doc Redmand and Joseph Bramlett.
Former world number one Sergio Garcia is among a group of 11 tied one further shot back after the first day with a round that included five birdies and an eagle for the Spaniard.
Three-time major winner Spieth, who is currently ranked 28th in the world, finished the day with an eagle on the 18th to grab a share of the lead alongside Spaun.
Dallas-born Spieth got off to a flying start with four birdies from his first six holes and five across the front nine, before holing a lengthy putt on the 18th much to the Texas crowd's delight.
Unheralded Californian 30-year-old Spaun also enjoyed an excellent opening day, birdying five of his first nine holes in a bogey-free round.
Another Texas native Scottie Scheffler finished with a five-under 67 while recent Masters winner Hideki Matsuyama carded a four-under 68.
World number three Jon Rahm also finished four-under, with fourth-ranked Bryson DeChambeau three-under and 2021 Masters runner-up Will Zalatoris a further shot back after a 70.