England’s Matt Wallace set the pace after a weather-delayed opening day at the CJ Cup Byron Nelson, where amateur Kris Kim impressed on his PGA Tour debut.
Wallace birdied five of his opening six holes on his way to a bogey-free 63 at TPC Craig Ranch, adding three more in his last eight holes to set the clubhouse target at eight under.
Former Ryder Cup winner Alex Noren and Canada's Taylor Pendrith are among the group a shot back, while defending champion Jason Day is within three of the lead after mixing seven birdies with two bogeys in an opening-round 66.
"It was great," Wallace said. "Got off to a great start. Three birdies to start any tournament is nice. Just a really solid round of golf. The wind started to pick up at the end, but the course is in amazing condition considering the rain."
Jordan Spieth started with a three-under 68, a score matched by Raul Pereda after a stunning hole-in-one at the par-three seventh, with 16-year-old Kim also within five of the lead after his start.
The English amateur, a sponsor's invite who is putting GCSE revision on hold to compete, posted five birdies and four bogeys before rounding off a memorable opening day with a chip-in eagle on his final hole.
"I thought it was pretty fun today," Kim said. "Made a lot of birdies, but couple bogeys in there as well. I think overall I played really well.
"They [nerves] were pretty high [at the first] to be honest, but helped that I got a good drive away and pretty good second shot in as well."
Compatriot Callum Tarren also opened with a 68 and Scotland's Robert MacIntyre started with a two-under 69, while Sungjae Im - who defended his title at the KPGA Tour's Woori Financial Group Championship last week - withdrew ahead of his opening round due to illness.
Watch the PGA Tour throughout the season live on Sky Sports! Early coverage from the CJ Cup Byron Nelson continues on Friday from 12.45pm on Sky Sports Golf ahead of full coverage from 9pm.
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