AP photo by David Becker / Keith Mitchell tees off on the 17th hole during the first round of the CJ Cup at Summit on Thursday in Las Vegas.

LAS VEGAS — Robert Streb went from simply making putts to wondering if he would ever miss Thursday in the CJ Cup at Summit. It led to his best start at any tournament and his lowest score on the PGA Tour.

And yet on this day at the Summit Club, his 11-under-par 61 was only good for a one-shot lead.

A world-class field lit up a very pretty and mostly defenseless golf course overlooking the Las Vegas Strip. The result was the lowest average score — 68.95 — for the opening round of a PGA Tour event in 2021.

Streb had 10 birdies and an eagle and led by one shot over Chattanooga native Keith Mitchell, who had more birdies than pars in matching his own low round with a 62. Harry Higgs was two strokes further back in third, with Hudson Swafford, Spain's Sergio Garcia and Norway's Viktor Hovland tied for fourth at 65. Such scoring in ideal conditions was what players were expecting on this Tom Fazio design, and 25 of 78 players in the field were at 67 or lower.

Mitchell, a 29-year-old former Baylor School and University of Georgia standout, missed the cut last week down the road at the TPC Summerlin and then spent five days working harder than most visitors to Las Vegas, and it helped that putting coach Ramon Bescansa was in town.

Mitchell made a 15-foot birdie putt on the par-5 third hole and was on his way. He followed with two more birdies from about that range and never let up on his way to a 10-birdie day.

"When that went in with good speed, I felt like I had a chance today," he said.

Good putting goes a long way on any course; keeping it on the grass on a course built in the desert also helps.

"If you hit the fairways, you have good chances. It's that simple," Mitchell said. "Because if you miss the fairways, the desert is a big penalty. It just depends on luck after that. ... If you get out of position out here, it can bite you."

Harris English — another former Baylor and Georgia standout also coming off a missed cut — did not fare well in the first round, making just four birdies against five bogeys for a 73 that left him tied for 70th.

Streb started with a pair of six-foot birdie putts and followed with a 12-footer for eagle. When he walked off the par-5 sixth hole after a long two-putt for birdie, he was 7 under already.

"I've never had a start like that, so it was kind of fun," Streb said. "I was trying to stay in the moment the best I can, and I don't know — you just feel like you can start aiming at stuff. Things seemed to be going my way."

Streb broke by two shots his previous low score on the PGA Tour, with one of those 63s in the 2016 PGA Championship on a rain-soaked course.