Cameron Tringale shrugged off a slow start to fire seven birdies in a three-under-par 69 and take a two-shot halfway lead in the US PGA Tour Texas Open.
Tringale, seeking his first US PGA Tour title, opened with back-to-back bogeys at TPC San Antonio, unable to get up and down from a greenside bunker at the 10th before finding a fairway bunker at 11.
But the American, who has made 11 cuts in 14 starts this season, strung together five birdies in a row from the 13th through the 17th, surging up the leaderboard to finish the day two strokes clear of former world number one Jordan Spieth and England's Matt Wallace.
Wallace had four birdies in his four-under par 68 for 137. Spieth joined him at seven-under with a 70 that featured four birdies and two bogeys.
It was a further two strokes back to another quartet of players on 139: South African Erik van Rooyen and Americans Kevin Stadler, Kyle Stanley and Brandt Snedeker.
Tringale's run of five straight birdies was his fourth in US PGA Tour competition, the most recent coming in his tie for third at the RSM Classic in November.
An 11-foot birdie putt at 13 launched the run and he rolled in a seven-footer at 14. He stuck his approach at 15 less than three feet from the pin for a birdie there, drained a four-footer at 16 and had another three-footer at 17.
"I knew I made a nice birdie on 13, a tough par three," Tringale said. "But then 14 was a pretty easy, easy hole today.
"Then I just hit a lot of really good iron shots to those holes. I think my furthest putt was four feet after 13, so just good approaches to the green. Still got to roll those in, but was able to do it."
Tringale, who teamed with Australian Jason Day to win the 2014 Franklin Templeton Shootout team post-season event, said his goal for the weekend would be to "keep doing what I'm doing."
Spieth, who has been knocking at the door of a first victory since his 2017 British Open triumph, made a bright start with birdies at the first and second.
He followed bogeys at 11 and 13 with birdies at 14 and 15 -- getting up and down from a green-side bunker at the 14th -- to keep himself in the hunt for a confidence-boosting victory with the Masters coming up next week.
"I thought two-under was a good score today and certainly could have shot lower," said Spieth after battling unpredictable afternoon winds.
"Was able to climb back from a couple bogeys on the back nine. It's kind of just stay in there, stay in there, stay in there and give yourself a chance come the back nine Sunday.
"That's really the best prep I can do for not only trying to win this golf tournament, but also for next week."