Shane Lowry hit sparkling form on the front nine at Torrey Pines to card an opening round 66 at the Farmers Insurance Open in San Diego which leaves him two shots off the lead.
The 36-year-old, who started his round on the North Course at the 10th, bounced back from successive bogeys to reel off six birdies in his final seven holes for a round of six-under-par which leaves him two shots off leader Kein Yu.
"I got off to a nice start and then made a couple of sloppy bogeys around the turn and managed to hole a few putts towards the end," said the Offaly native.
"I just kept telling myself I was playing good golf, hitting some nice shots and got rewarded towards the end.
"I haven't been here since 2018 and historically you need to make your score on the North Course and then hang in a little bit on the South Course and take your chances when you get them.
"But I didn't know what I was going to play like. I just went out there to play the golf course that was in front of me and hit as good a shot as I could and thankfully today that was good enough."
Competing on the South Course, compatriot Seamus Power endured a more challenging afternoon.
The Waterford native began with nine successive pars, and his first birdie came at the last, by which time he had bogeyed 11, 12 and 15.
The North and South courses at Torrey Pines are both used for the first two rounds before the final 36 holes are played on the south course on Saturday.
Taiwan's Yu fired eight birdies as he took a one-shot lead. He carded a bogey-free 64 on the North Course, a birdie at the last edging him ahead of America's Patrick Cantlay and Japan's Ryo Hisatsune.
A further shot back, Lowry is joined in a tie for fourth by former Masters champion Hideki Matsuyama, Germany's Thomas Detry, Englishman Aaron Rai and Alejandro Tosti of Argentina.
Nicolai Hojgaard, who finished seventh at the Dubai Desert Classic, and America's Nick Hardy were the best of those who started on the more difficult South Course - their 67s leaving them amid a large group on five-under-par.
Hojgaard's first start as a full-time member of the PGA Tour came despite jetlag and just nine holes on the North Course in practice.
"You've got to try to find a way," the Danish Ryder Cup star told the PGA Tour website. "I'll just push myself until we feel like the jetlag's gone."
"I think sometimes you can take advantage of not knowing the golf course and you're just thinking about your execution. I felt like that was the only thing I was doing today."
