Phil Mickelson fired a career best-equalling 60 to take the early lead as he made his 2019 debut at the Desert Classic in California.
The five-time major champion shot 10 birdies and an eagle during a blemish-free day on the par-72 course at La Quinta.
The 48-year-old, with two previous 60s at the Waste Management Phoenix Open in 2005 and 2013, hit his best ever career round to par and put himself top of the pack on 12 under.
The American narrowly missed shooting his first ever round of 59, needing two birdies on the last two holes to reach the feat. He made par on the 17th before holing a birdie from 10 feet on the 18th.
In a video posted on the PGA Tour’s Twitter page, Mickelson said after his round: “I really didn’t think this was going to be a day when I would go low. I came in with very low expectations.
“I haven’t had a lot of time to practise and prepare. I felt like all areas were OK, but you never really know until you get out and play and compete.
“The good thing was I made a couple of bad swings and I got away with them.”
The tournament is held over three courses — La Quinta, the Nicklaus Tournament Course and PGA West’s Stadium Course.
Mickelson’s closest challenger, compatriot Adam Long, is three shots off the pace after carding a nine-under 63 on the Nicklaus course.
Englishman Justin Rose, the world number one, finished tied for 31st on four-under after an opening round 68 at La Quinta, while Scot Martin Laird sits in joint fourth on seven-under after mixing two bogeys and nine birdies for a round of 65 at Nicklaus.
The opening day wasn’t that much fun for Ireland’s Séamus Power as he opened with a two-over 74 on the Stadium Course.
Collated first round in the USPGA Tour The Desert Classic, Stadium Course, La Quinta, California, United States of America (USA unless stated, Irish in bold):
La Quinta (Par 72):
60 Phil Mickelson (USA)
64 Curtis Luck (Aus)
65 Wyndham Clark (USA)
66 Abraham Ancer (Mex), Jon Rahm (Spa), Adam Svensson (Can), Robert Streb (USA)
67 Daniel Berger (USA), Cameron Davis (Aus), Chez Reavie (USA)
68 Wes Roach (USA), Harold Varner III (USA), Benjamin Silverman (Can), Lucas Glover (USA), Aaron Wise (USA), Sam Saunders (USA), Michael Thompson (USA), Justin Rose (Eng), Sam Burns (USA), Josh Teater (USA)
69 Bud Cauley (USA), Ryan Palmer (USA), Beau Hossler (USA), Ryan Armour (USA), David Hearn (Can), Brady Schnell (USA), Johnson Wagner (USA)
70 Brian Stuard (USA), Peter Malnati (USA), Tom Lovelady (USA), Andrew Putnam (USA), Scott Stallings (USA), Cooper Musselman (USA), Cody Gribble (USA), Bronson Burgoon (USA)
71 Luke List (USA), Zach Johnson (USA), John Chin (USA), Chase Wright (USA), Jamie Lovemark (USA), Mike Weir (Can), Sungjae Im (Kor), Corey Conners (Can)
72 Ben Crane (USA), Pat Perez (USA), Russell Henley (USA), Scott Piercy (USA)
74 Jason Gore (USA)
75 Charles Reiter (USA), Danny Willett (Eng)
76 Whee Kim (Kor)
77 Kyle Jones (USA)
PGA Stadium West (Par 72):
65 Adam Hadwin (Can)
66 Adam Schenk (USA), Steve Marino (USA), Jhonattan Vegas (Ven)
67 Talor Gooch (USA), Jose de Jesus Rodriguez (Mex), Tom Hoge (USA)
68 Nick Watney (USA), JT Poston (USA), Joey Garber (USA), Anders Albertson (USA), Jim Herman (USA)
69 Chris Stroud (USA), Robert Garrigus (USA), J.J. Spaun (USA), Chesson Hadley (USA), John Catlin (USA)
70 Stephan Jaeger (Ger), Roger Sloan (Can), Hank Lebioda (USA), James Hahn (USA), Nick Taylor (Can), Kevin Streelman (USA), Anirban Lahiri (Ind)
71 Charley Hoffman (USA), Peter Uihlein (USA), Matt Jones (Aus), Roberto Diaz (Mex), John Senden (Aus), Roberto Castro (USA)
72 Carlos Ortiz (Mex), Scott Brown (USA), Bill Haas (USA), Sam Ryder (USA), Nate Lashley (USA), Tyrone Van Aswegen (Rsa), Mark Wilson (USA)
73 Brian Harman (USA), Sebastian Munoz (Col), Tyler Duncan (USA), Russell Knox (Sco), Fabian Gomez (Arg), D.J. Trahan (USA)
74 Charl Schwartzel (Rsa), Séamus Power (Irl)
75 Shawn Stefani (USA), Rod Pampling (Aus), George Cunningham (USA)
76 Hunter Mahan (USA), Will MacKenzie (USA), Michael Block (USA)
78 Chris Kirk (USA)
Nicklaus Tournament Course (Par 72):
63 Adam Long (USA)
65 Trey Mullinax (USA), Martin Laird (Sco)
66 Sean O’Hair (USA), Cheng-Tsung Pan (Tai), Alex Cejka (Ger)
67 Kramer Hickok (USA), Ryan Blaum (USA), Patrick Cantlay (USA), Dominic Bozzelli (USA), Nicholas Lindheim (USA), Alex Prugh (USA), Charles Howell III (USA)
68 Max Homa (USA), Rory Sabbatini (Svk), Denny McCarthy (USA), Vaughn Taylor (USA), Andrew Landry (USA), Martin Piller (USA), John Huh (USA)
69 Brendan Steele (USA), D.A. Points (USA), Joaquin Niemann (Chi), Chad Collins (USA), Kevin Kisner (USA)
70 Jim Knous (USA), Scott Langley (USA), Martin Trainer (USA), Si Woo Kim (Kor), Cameron Tringale (USA), Harris English (USA)
71 Julian Etulain (Arg), Aaron Baddeley (Aus), Jason Kokrak (USA), Ollie Schniederjans (USA), Hudson Swafford (USA), Brian Gay (USA), Kyoung-hoon Lee (Kor), Jonathan Byrd (USA), Brandon Harkins (USA)
72 Patton Kizzire (USA), Seth Reeves (USA), Dylan Frittelli (Rsa)
73 Richy Werenski (USA), Derek Fathauer (USA), J.J. Henry (USA), Sepp Straka (Aut), Sang-moon Bae (Kor), Brandon Hagy (USA)
75 Chris Thompson (USA)
77 Grayson Murray (USA)
79 Jason Dufner (USA)