Mathis jumped to the top of the leaderboard late in the day, finishing with six birdies and one late bogey. He is back on the PGA Tour for a second time thanks to finishing 13th on the Nationwide Tour money list last year.
Keegan Bradley and Fabian Gomez each had 67s. Bradley is among the few here who could play their way into the U.S. Open by winning at the TPC Southwind for a second Tour victory since the last Open. Bradley won the Byron Nelson Championship two weeks ago.
The 37-year-old Mathis has been playing golf since turning pro in 1997 after leaving Campbell University. He started playing mini tours and was on the Canadian Tour before switching to the Nationwide circuit. He first joined the PGA Tour in 2009 when he posted a pair of top-25 finishes, including a tie for 23rd in Memphis.
But he wound up back on the Nationwide Tour last year. St. Jude is his 14th event on the PGA Tour this year with five missed cuts.
The native of Winston-Salem, N.C., credited a visit with his coach Patrick Kelley this week for helping straighten out his line when putting. He noticed the difference almost immediately when he started on the back nine and rolled in a 9-footer to save par.
Then he added a birdie putt on the par-3 No. 11 from just inside 19 feet, plus 8-footers for birdies on Nos. 13 and 16. He had a 15-footer for birdie on No. 2 from a fairway bunker to join the pack tied at 4 under.
Mathis had the lead to himself when he hit a wedge on the par-5 No. 3 to within 13 feet, then made another birdie. He padded his advantage with a four-footer on No. 5 for his sixth birdie.
His lone bogey came on No. 8, when he three-putted from within 8 feet.
Karlsson started off the front nine with three birdies on his first six holes. But the Swede hit his tee shot on the par-4 No. 13 into a fairway bunker and wound up bogeying the hole to fall back to 2 under.
He got the stroke back with a birdie on the par-3 No. 14, rolling in from 18 feet. He also had a 19-footer for birdie on No. 15, but came up a couple feet short.
Merrick has made six of eight cuts this year, with his best finish a tie for 11th at Puerto Rico. He took advantage of an early tee time to take the early clubhouse lead.
He said the key Thursday was hitting shots closer to the hole.
“It’s definitely been something that’s been hurting me,” he said. “I’ve been hitting greens but not really getting it close. Today I hit some good shots and had some decent looks at birdies that were inside 10 feet.”
Kisner is a rookie in his 13th event on Tour this season. He started this tournament with only his fourth round in the 60s this year, taking advantage of a morning tee time with little wind. The South Carolina native who went to the University of Georgia hasn’t finished better than a tie for 39th, and Kisner said his biggest challenge is learning the courses.
“The courses are much more difficult than the Nationwide,” he said. “You really have to know where you’re going to miss it and places to be. It’s all just part of learning. It’s why they call you a rookie.”
DIVOTS: Sergio Garcia may have a chance for an early arrival at Congressional. He opened with a 78 that featured an 11 on the par-5 No. 3. Garcia was 2 over for the back nine before hitting three times into the water running along much of the right side of the third fairway. He hit his ninth shot into a greenside bunker before blasting out to within 3 feet and finally sunk that putt for his 11. … J.B. Holmes did not start.