Patrick Reed started strongly while Alex Noren finished well as the pair took the opening-round lead at the Farmers Insurance Open in California.
Starting his tournament on the back nine, American Reed was locked in from his opening drive, stringing together three straight birdies before adding a fourth on the 17th to head into the turn at four under.
He then picked up another four shots on the back nine to finish Thursday’s opening round with a bogey-free score of eight-under 64.
Reed shares a one-shot lead with Sweden’s Noren, who also started on the North Course’s back nine. Noren birdied the 10th and 14th before soaring up the leaderboard with an eagle on the 17th.
A bogey on the next hole threatened to derail his momentum, but Noren recovered well to add five more birdies on the front nine.
Trailing the pair is American Scottie Scheffler, who finished seven-under on the back of five birdies and an eagle on the 16th.
Ireland's Rory McIlroy had a strong start on the South Course to close out Thursday at four under. He sits at equal-21st alongside England's Tom Lewis.
Collated first round scores (USA unless stated, par 72):
64 Alexander Noren (Swe), Patrick Reed
65 Scottie Scheffler
66 Sam Burns, K. J. Choi (Kor), Rhein Gibson (Aus), Talor Gooch, Lanto Griffin, Brandon Hagy, Beau Hossler, Luke List, Peter Malnati, Ryan Palmer, Cameron Smith (Aus), Gary Woodland
67 Wyndham Clark, Will Gordon, Denny McCarthy, Adam Scott (Aus), Tim Wilkinson (Nzl)
68 Cameron Champ, Lucas Glover, Si Woo Kim (Kor), Anirban Lahiri (Ind), Tom Lewis (Eng), Rory McIlroy (Irl), Seung-Yul Noh (Kor), Roger Sloan (Can), Robert Streb, Kevin Streelman, Will Zalatoris
69 Joseph Bramlett, Bronson Burgoon, Tony Finau, Adam Hadwin (Can), John Huh, Sung Jae Im (Kor), Michael Kim, Grayson Murray, J. T. Poston, Jon Rahm (Spa), Brandt Snedeker, Jordan Spieth, Scott Stallings, Sepp Straka (Aut), Kevin Tway, Richy Werenski
70 Sebastian Cappelen (Den), Cameron Davis (Aus), Rickie Fowler, Dylan Frittelli (Rsa), Doug Ghim, James Hahn, Tom Hoge, Viktor Hovland (Nor), Mackenzie Hughes (Can), Matt Jones (Aus), Jason Kokrak, Martin Laird (Sco), Ryan Moore, Matthew NeSmith, Xander Schauffele, Charl Schwartzel (Rsa), Jhonattan Vegas (Ven), Bubba Watson, Xinjun Zhang (Chn), Andres Gonzales, Jared du Toit (Can)
71 Scott Brown, Fabian Gomez (Arg), Harry Higgs, Max Homa, Russell Knox (Sco), Satoshi Kodaira (Jpn), Marc Leishman (Aus), Troy Merritt, Phil Mickelson, Cameron Percy (Aus), Pat Perez, Ted Potter Jr., Sam Ryder, Kevin Stadler, Brian Stuard, Justin Suh, Tain Lee, Rafael Campos (Pur), Bill Haas
72 Byeong-Hun An (Kor), Chris Baker, Corey Conners (Can), Bo Hoag, Brooks Koepka, Francesco Molinari (Ita), Andy Ogletree, Louis Oosthuizen (Rsa), Rob Oppenheim, Carlos Ortiz (Mex), Patrick Rodgers, Rory Sabbatini (Svk), Chase Seiffert, Kyle Stanley, Steve Stricker, Cameron Tringale, Kristoffer Ventura (Nor), Vincent Whaley, Jim Knous
73 Tyler Duncan, Chesson Hadley, Kramer Hickok, Kelly Kraft, Hank Lebioda, Nelson Ledesma (Arg), Kyle Mendoza, Henrik Norlander (Swe), Doc Redman, Robby Shelton, Ben Taylor (Eng), Jimmy Walker
74 Jason Dufner, Scott Harrington, David Hearn (Can), Danny Lee (Nzl), Kyoung-Hoon Lee (Kor), Hideki Matsuyama (Jpn), Maverick McNealy, J. J. Spaun, Erik van Rooyen (Rsa), Nick Watney, Cameron Young, Michael Gellerman, Willie Mack III
75 Charley Hoffman, J. B. Holmes, Adam Schenk, Aaron Baddeley (Aus)
76 Jason Day (Aus), Emiliano Grillo (Arg), Billy Horschel, Hunter Mahan, Tyler McCumber, Matthew Every, John Senden (Aus)
77 Ryan Brehm, Keith Mitchell, Ty Strafaci, Martin Trainer
78 Mark Anderson, Joel Dahmen, Harold Varner III, Matthew Wolff, Seamus Power (Irl)
79 Harris English, Michael Gligic (Can), Jamie Lovemark
80 Charles Howell III, Camilo Villegas (Col)