IRVING, Texas -- When the heat was on and the huge throng following hometown-favorite Jordan Spieth was at its most raucous on Saturday in the third round of the AT&T Byron Nelson, Brooks Koepka was at his best.
It took everything Koepka had to survive his pairing with Spieth and forge a two-shot lead at TPC Four Seasons Las Colinas in a round played under sunny, flawless conditions.
Koepka's 5-under-par 65 in the third round pushed him to 16-under 194 through 54 holes, as Spieth posted a 67.
Koepka had seven birdies and two bogeys on Saturday while Spieth had five birdies and two bogeys and shot even-par on the back nine, making a bogey on the final hole.
"Jordan's got a lot of support here, which is cool to see, but he should -- he's grown up here and it's his hometown," Koepka said. "There are so many people out there cheering him.
"I really don't care -- it doesn't bother me."
Kyle Reifers was alone in sixth, four shots behind, after a 65, while Tom Wilkinson shot a third round-best 63 and was another stroke down in a tie for seventh with Gary Woodland (64), Steve Marino (66) and Bryce Molder (68).
Second-round leader Ben Crane posted a 72 and was six shots back in a tie for 11th.
"It's nice to go into the final round with a two-shot lead," Koepka said. "Today I hit the ball terrible. It wasn't anything to brag about at all. But I feel like I'm putting into an ocean right now.
"We switched putters two weeks ago and it's got a real soft feel, rolls right away. We've worked hard over the last year trying to improve the short game and putting, and it let me hang in there today."
The tenor of the third round changed in a 10-minute afternoon stretch on holes 14 and 15.
Spieth held a one-stroke lead over Koepka and Cauley when he stepped to the tee at the par-4 14th but he hit his drive into the water to the left of the fairway.
After a drop and a one-stroke penalty, he chipped out into the fairway and then hit a sloppy shot over the water that ended up on the green 23 feet from the hole.
Somehow, Spieth managed to roll in the ensuing putt for bogey.
Koepka, on basically the same line as Spieth for his 20-foot birdie putt, poured it in to complete a two-shot swing, turning a one-stroke deficit into a one-shot lead.
One hole ahead at the 15th, Cauley canned a twisting 12-foot par putt to stay within a stroke of the lead.
"I was in some really, really tough spots and it was a very stressful round of golf to play because I just don't have confidence over the ball right now," Spieth said.
"It's very frustrating and actually I'm putting incredible to still be in this tournament."
Koepka expanded his lead to two strokes on the par-5 16th when he chipped his third shot from right of the green to within two feet and converted the birdie chance.
Spieth also had an opportunity for birdie, but lipped out an eight-foot putt. He made the best of another chance at the par-3 17th with a 19-foot birdie putt that cut Koepka's advantage back to a single stroke.
"That reaction after Jordan made his putt on the 17th was probably the loudest roar I ever heard on a golf course, which is pretty neat," Koepka said.
Spieth admitted that he was a little overwhelmed by the crowd's outpouring of affection on the 17th green.
"That's a moment that I'll never forget," he said. "Even though it's Saturday and may or may not have any impact on this tournament, that was the coolest roar I've ever heard.
"There's nothing I could do after but just start smiling. That was really, really cool."
Koepka got the stroke back on the par-4 18th when he sank a nerveless 10-foot par putt and Spieth missed his par putt from nine feet after slicing his tee shot into the woods to the right of the fairway.
"I've got to find at least a ball flight that I can play to where I don't have to try and hit iron off the 18th tee because I don't know where the woods are going to go," Spieth said.
"It's something that I can certainly get by the time I tee off tomorrow with the right feel on the range and at least seeing a couple of them on the golf course."
Cauley was at his best in the middle of the round but lost some momentum with poor iron play down the stretch.
"I got off a little squirrely but I had some nice up and downs early on," Cauley said. "I had some birdies there before the turn and after and I missed a few iron shots coming in.
"All in all, I played pretty solid."
NOTES: Defending champion Steven Bowditch of Australia made the 36-hole cut on the number at 2-under 138 with rounds of 68-70, snapping a streak of five consecutive missed cuts. However, he shot 75 on Saturday and missed the 54-hole cut. ... Matt Kuchar has yet to miss a cut in nine starts at the AT&T Byron Nelson (T39-2007, T42-2008, T39- 2009, T6-2011, T15-2012, T33-2013, T7-2014, T39-2015, TBD-2016). Kuchar finished tied for third last week at the Players Championship, his best finish since a tie for second at the 2015 CareerBuilder Challenge in February. ... Six past AT&T Byron Nelson winners were in the field this week: Sergio Garcia, Jason Dufner, Steven Bowditch, Keegan Bradley, Ernie Els and Brendon Todd. Bradley, Els and Todd missed the cut. ... Garcia went the first 44 holes of the tournament without a bogey before he three-putted on the ninth hole on Saturday.