Patrick Reed and Alex Noren carded eight-under 64s to share the lead after the opening round of the Farmers Insurance Open.
Reed, who missed the cut at last week's The American Express, produced a bogey-free first round on the North Course at Torrey Pines on Thursday.
The American made three straight birdies after starting his round at the 10th and had another run of three straight on his back nine, tying the second-lowest first-round score of his PGA Tour career.
Reed shares a one-stroke lead with Noren, the 2018 runner-up who also fired a 64 on the North Course.
A former top-10 player, Noren has dropped to 96th in the rankings after going winless since 2018.
Scottie Scheffler is outright third after his 65, while 12 players opened with 66s – with only Peter Malnati and Ryan Palmer, who was runner-up alongside Noren three years ago, playing the South Course of that group.
K.J. Choi, 50, is also among that group after a bogey-free round that featured six birdies, as the two-time runner-up – whose last win was in 2012 – surprised.
Beau Hossler, Talor Gooch, Luke List, Sam Burns, Gary Woodland, Lanto Griffin, Rhein Gibson, Cameron Smith and Brandon Hagy are also tied for fourth.
Rory McIlroy made a solid start with a four-under 68 on the South Course, while 2017 winner Jon Rahm and Jordan Spieth opened with 69s.
Brooks Koepka is in a tie for 88th after an even-par 72, while two-time champion Jason Day endured a tough opening round, mixing a double bogey with six bogeys and four birdies to shoot a 76.
Richy Werenski, meanwhile, carded a 69 that included a hole-in-one at the third hole on the South Course, having also managed an ace in the final round of last year's event.