The former World No.1, who spent a year at University of Nevada (Las Vegas) as a teenager, shot a bogey-free round with birdies on holes 1, 10, 14, 15 and 16.

US-based Australian amateur and current UNLV star Jack Trent (67) is one shot adrift of his idol following a solid PGA Tour debut.

The 20-year-old's round was up and down, carding seven birdies along with three bogies at TPC Summerlin.

After an opening-hole bogey on the par-4 10th, Trent peeled off five birdies before dropping another shot. He finished his round bogey-birdie-bogey-birdie.

"First tee nerves got me," Trent told the Golf Channel.

"Bounced back with a birdie and after that really started to settle in."

Trent is playing on a sponsor exemption this week thanks to his victory at the Southern Highlands Collegiate.

The man they're chasing is Canada's Nick Taylor (63) who went on an impressive six-hole stretch on the back-nine at six-under par which included four birdies and an eagle.

"The first two holes, I actually hit pretty good drives. Had a little bit of mud on it, so the ball just kind of took off oddly," 31-year-old Taylor said.

RIGHT: Taylor leads by  shots after the opening round in Las Vegas. PHOTO: Tom Pennington/Getty Images.

"Was able to make two good par saves, and from there was able to hit a bunch of greens, make some putts."

Brian Harman is one stroke off the pace, while Phil Mickelson, who missed the cut last week at the Safeway Open in his season debut, had his lowest round since late February and is one of five Americans tied for third. Mickelson shot a 65 along with Brian Gay, Sam Ryder, Brian Stuard and Maverick McNealy.

Defending champion Bryson DeChambeau had a solitary blemish on the par-4 7th in his round of 66.

2016 winner Rod Pampling shot four-under 67, as did fellow Aussie Aaron Baddeley, while compatriots Matt Jones (68), Cameron Smith (69) and Cameron Percy (72) are all hoping to feature in the weekend action.

Brooks Koepka, who had stem cell treatment on his left knee on August 25 after the FedExCup ended, began his season by needing two birdies over the last four holes to break par.

Koepka is the first No.1 player in Las Vegas since Greg Norman in 1988.