Playing in the final group of the day off the first tee, the 32-year-old Mexican player birdied four of the first five holes, eagled the par-5 10th and birdied three of the last five in the bogey-free round at TPC Deere Run. He took the lead with a 12-foot birdie putt on the par-3 16th.
“I just feel that everything clicked,” Diaz said. “I’ve been playing pretty solid throughout the year. The driver has been awesome. I’ve been hitting a lot of fairways, and today I hit good numbers all day, and that helps.”
Winless on the PGA Tour, Diaz tied for eighth at the Travelers Championship last month.
Americans Adam Long and Russell Henley were two strokes back. Martin Laird was another stroke back at 65 with Ryan Palmer, Andrew Landry, Vaughn Taylor, Zack Sucher and Ryan Blaum.
Long, who got his first career win earlier this season at the Desert Classic, had eight birdies – four on the front nine and four on the back nine.
Henley has missed the weekend cuts in his last four straight starts. But he highlighted an impressive birdie run by drilling a 55-foot putt on the par-3 7th hole.
“I don’t think I’ve ever lost the belief that I can have a nice tournament,” Henley said. “It’s just a matter of a few bumps here and there.”
Scotland’s Laird, who skipped his national tournament this week in an effort to boost his playoff positioning, followed up a 65 to close out last week’s event in Minnesota with birdies on five par 4s on Thursday.
Palmer, the second-highest ranked player in the FedEx Cup standings in the field at No. 22, returned from a month-long family vacation with a strong round.
Palmer was somewhat inconsistent on his front nine before rallying for three birdies in a five-hole stretch.
“Stress-free today, it felt like. Being off for four weeks, travelling the world a little bit was fun. But I just came into the week just wanting to get my game back going for next week obviously,” Palmer said.
Twenty-year-old rookie Matthew Wolff, who picked up his first career win at the 3M Open last week, opened with a 67. Wolff, the youngest winner on the tour since Jordan Spieth won at Deere Run six years ago, hit 15 greens in regulation and played bogey-free.
“Having that PGA Tour card locked up is a lot of weight off of my shoulders,” Wolff said. “Everything in my game feels really good right now.”
Nick Taylor of Abbotsford, B.C., is the top Canadian after a 4-under 67.
Roger Sloan of Merritt, B.C. (68) finished 3 under, David Hearn of Brantford, Ont. (69) is 2 under, Mackenzie Hughes of Dundas, Ont., and Adam Svensson of Surrey, B.C. (70) are 1 under, while Ben Silverman of Thornhill, Ont., (71) is even. Austin Connelly, an American-Canadian dual citizen, shot a 1-over 72.
Defending champion Michael Kim, who set the tournament record at Deere Run a year ago by winning by eight shots, had a 73. Kim has made just five of 28 cuts since winning in the Quad Cities.
Local favourite and past tournament champion Zach Johnson saw a streak of 40 consecutive rounds of even par or better at Deere Run come to an end after a 1-over 72. Johnson, who last shot over par there in 2008, missed a long birdie putt that would’ve kept the streak alive by inches.
“Frustrating. I mean, the good shots that I hit I didn’t get anything out of it and the bad ones were, I’m scrambling a little bit,” Johnson said.
Full scoring can be found here.