Jordan Spieth fired a one-under par 69 to seize a one-stroke lead over fellow Americans Patrick Reed and Troy Merritt after Friday's second round of the US PGA Travelers Championship.
Sixth-ranked Spieth, the 2015 Masters and US Open champion seeking his 10th tour title, stood on eight-under par 132 after 36 holes at TPC River Highlands near Hartford, Connecticut.
Reed opened and closed with birdies in firing a 66 while Merritt shot 68 to stand on 133 with compatriots Wesley Bryan, Daniel Summerhays, Boo Weekley and Chase Seiffert another stroke adrift.
Spieth, who began on the back nine, birdied the par-4 12th but pulled his tee shot well left at the par-5 13th and took a penalty stroke on the way to a double bogey.
"I was a little tentative to start," Spieth said. "I had a double cross off the tee at the par-5, made double, but responded nicely."
Spieth answered with a four-foot birdie putt at the par-4 15th, then birdied the first and third holes, the latter from 35 feet.
"It was nice to see as many of those putts as possible go in to give me some confidence for the weekend," Spieth said.
A final stumble for Spieth came at the par-4 fifth, blasting out from a bunker but missing a seven-foot par putt.
"Things were just a little bit off today," Spieth said. "I didn't feel like it was harder than yesterday. Just had an off round. Was able to hold it at one-under instead of falling further back."
Reed opened with a 24-foot birdie and closed with a 13-foot birdie putt to grab a share of second with Merritt, a back-nine starter who made bogey at 16 but birdied 17 and 18, the latter from 31 feet, and the fourth to make his move.
"Really it was just staying patient," Reed said. "Even with the wind blowing, you'll have your chances. I was able to keep the ball in play and make some putts."
Canada's Graham DeLaet reached nine-under for the tournament in his second round thanks to back-to-back birdies at the par-5 sixth and par-4 seventh and again at the par-3 11th and par-4 12th, sinking a 35-foot par putt at 11 and a 15-footer at the 12th.
But he found the water off the tee at the par-5 13th and made double bogey, then made another double bogey at 18 after finding a bunker on his approach, finishing on 70 for the round and three adrift of Spieth in a pack on 135.
Third-ranked Rory McIlroy fired a 73 to finish on 140, making the cut on the number. The Northern Ireland star, a four-time major champion, made bogeys at the par-3 fifth and 11th holes. He missed the green and a nine-foot par putt on the fifth, then found bunkers on 111 and 12 on the way to bogeys.
McIlroy birdied 14 and 15 but fell back with bogeys on 16 and 18.
World number four Jason Day of Australia missed the cut, firing four bogeys and four birdies for a 70 to stand on 142.