England's Paul Waring stunned the field with a bogey-free 63, setting the pace at seven-under 63 at Memorial Park Golf Course. The 41-year-old, who has struggled to break into the top 300, posted his lowest career round on the PGA Tour, signaling a potential breakthrough. His performance has significant implications, as the Texas Children's Houston Open is a critical stop for players seeking a spot in The Masters.

Gary Woodland is one off the lead after a birdie-birdie finish to his six-under 64, with Sam Burns sharing third spot with fellow Americans Tom Hoge and Michael Brennan. English duo Marco Penge and Matt Wallace are both within three of the lead after four-under 66s, while Cole Hammer is also in contention after posting a hole-in-one at the par-three 15th during a low-scoring opening day.

Chris Gotterup - the highest-ranked player in the field - and defending champion Min Woo Lee are both five off the pace after carding opening-round 68s, while Shane Lowry is a further shot back after a final-hole birdie helped him to a one-under 69. Brooks Koepka was two under after five holes of his opening round but stumbled with three double-bogeys in a four-hole stretch around the turn, with a five-over 75 leaving the five-time major champion in danger of missing the cut.