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LAS VEGAS (AP) -- Peter Uihlein topped the leaderboard at 8-under 63 on Thursday in the Shriners Hospitals For Children Open, with Jordan Spieth three strokes back in his season debut.

Uihlein birdied six of his final nine holes in the morning round at TPC Summerlin.

"It's nice to get off to a good start, especially when there wasn't much wind," Uihlein said. "I've heard mixed reviews on the forecast this week, so nice to get off to a good start and take advantage of good conditions early."

Seth Reeves shot 64, electing to finish the par-5 ninth after the horn sounded suspending play because of darkness. Harold Varner III and Robert Streb were two strokes back at 65.

Spieth shot 66 in his first career start in a domestic fall event.

"It's gettable without the wind," Spieth said. "We got really, really good conditions this morning, so and 8 under, certainly thought that was out there. To see Peter shoot that was no surprise. Then the guys in the afternoon are going to have it tougher. Looks like we might get the good end of the draw. It's always nice having a little bit of luck in Vegas, right?"

Fellow U.S. Ryder Cup player Bryson DeChambeau also was at 66 with Si Woo Kim, Whee Kim, Sebastian Munoz, Sam Ryder and Abraham Ancer.

"It was a good round for sure," DeChambeau said. "Unfortunately, had a couple three-putts and had some missed opportunities, but I'm a little rusty on the putting green."

DeChambeau and Spieth joined losing Ryder Cup teammates Webb Simpson, Tony Finau and Rickie Fowler and U.S. captain Jim Furyk in the field. Fowler and Simpson shot 68s in the same group, Finau had a 69, and Furyk a 71.

Spieth is playing for the first time since the Ryder Cup and making his first stroke-play start since the BMW Championship in early September.

"It's been really the last kind of six tournaments or so of the regular season, too, I started to clean up kind of in the setup and vision," Spieth said. "It's getting close to where I feel like I can just kind of point, aim, shoot, which is where I want to be."

Uihlein opened on the back nine, backing birdies on Nos. 11, 14 and 15. Riding a hot putter on the second nine, he birdied the first four holes, added another on No. 6, bogeyed the par-4 seventh and rebounded with a birdie on the par-5 ninth.

"I hadn't been putting great the first few weeks of the season," Uihlein said. "I put in a lot of work last week for a few days and switched putters, so it's nice to kind of see that hard work kind of pay off this quickly. Wasn't really expecting it."

The son of Acushnet/Titleist chairman and CEO Wally Uihlein, the 29-year-old former Oklahoma State player is winless on the PGA Tour. He won the 2010 U.S. Amateur, took the European Tour's 2013 Madeira Islands Open and the Tour's 2017 Nationwide Children's Hospital Championship.

"I've always believed the game of golf is more of a marathon and a journey and not a sprint," Uihlein said. "It's one of those things, if you keep working hard, keep your head down, keep focused, stay disciplined, results will follow. You're not really trying to press or force anything."

DIVOTS: Defending champion Patrick Cantlay was at 69. Cameron Champ, the Sanderson Farms winner last week in Mississippi, also shot 69. He played alongside Spieth. ... Hall of Famer Davis Love III shot 70. Love won the event in 1993, the year Spieth was born. He lost in a playoff in 1996 to Tiger Woods, the first of 80 tour victories for Woods. Fellow PGA Tour Champions player Kenny Perry shot 73. ... J.J. Spaun opened with a 67, playing for the fifth consecutive week. He's the only player not to miss a tournament since the season began Oct. 4. ... Freddie Jacobson also had a 73 in his return from hand surgery. He played for the first time since the 2017 Byron Nelson.