Wyndham Clark carded a flawless 64 to take a one-shot lead after the opening round of the Waste Management Phoenix Open, but Ireland's Seamus Power saw his momentum unravel with a costly triple bogey.
Power was three under going into the final hole of his round after birdies on 13, 14 and 16.
But the Waterford native twice found the water with tee shots on the 18th, with the eventual triple bogey wiping out all his gains from earlier in the day and his 71 leaving him seven shots off Clark's lead.
Meanwhile, Clark opened with a birdie and added another two on holes eight and nine.
The American's momentum continued after the turn with another pair of birdies before capping off his round by picking up shots on the 13th and 15th.
Speaking after the round, Clark told reporters: "You can't necessarily control the score and what happens to your golf ball, but you can control your thoughts.
"So it was a good reminder for me to get back to, hey, when I'm playing my best, I look at the glass more half full than I do half empty."
His seven-under-par round puts him one shot in front of the chasing duo of compatriots Taylor Moore and Lee Hodges.
Two-time major champion Justin Thomas is among a group of six players sitting a shot further back.
Round one play will conclude on Friday morning after play was suspended due to darkness.
Additional reporting: PA
