New York - Defending champion Jordan Spieth stumbled to a three-over par 73 to fall from a share of the lead in Friday's second round of the US PGA Travelers Championship while Rory McIlroy hung tough.
Reigning British Open champion Spieth, who fired a first-round 63, took a triple-bogey eight at the par-five 13th, his fourth hole of the day, and added three bogeys, an eagle and a lone birdie to stand on four-under 136.
McIlroy, a back-nine starter like Spieth, began the day one off the lead and shot 69 to stand on 133, three strokes adrift of leader Brian Harman, a US left-hander who followed his opening 64 with a 66.
"I left a few out there. I didn't hit the ball as good as I did yesterday. Still hit it okay, but I felt like I had a lot of good putts that just didn't go in," said McIlroy.
"Over the weekend, if I just keep giving myself chances, hit a few more fairways than I did today, and if I can keep doing that and keep giving myself chances, hopefully I'll be able to move."
Spieth put his tee shot left of the cart path at 13 and took a penalty stroke, then put his fourth shot into water. He finally reached the green in six and two-putted from 23 feet (three meters) for triple bogey.
He found water again off the 15th tee and put his third shot into deep rough on the way to bogey.
Spieth answered by sinking a 13-foot birdie putt at the first hole but took bogeys after finding the rough off the second tee and a greenside bunker at the fourth, falling to the projected cut line.
But the three-time major winner responded with a tap-in eagle at the par-five sixth, putting his second shot inches from the cup.
McIlroy, a four-time major champion, found a greenside bunker off the tee at the par-four 15th, blasted out to five feet and sank a birdie putt. He sank an 18-foot birdie putt at the second but took his lone bogey at seven after missing a six-foot par putt.
Harman, a runner-up at last year's US Open, seeks his third US PGA crown after the 2014 John Deere Classic and last year's Wells Fargo Championship.
Harman also began on the back nine and made three bogeys and three birdies before the turn, then birdied four of the first seven holes on his second nine of the day, the most impressive of them on a 25-foot birdie putt at the par-four fourth.
Harman has a one shot lead over Matt Jones (66), Russell Henley (65) and Zach Johnson (68) who are tied for second at nine-under 131.
Scores after Friday's second round of the US PGA Travelers Championship (par 70, USA unless noted):
130 - Brian Harman 64-66
131 - Matt Jones (AUS) 65-66, Russell Henley 66-65, Zach Johnson 63-68
132 - Bryson DeChambeau 66-66, Paul Casey (ENG) 65-67, Beau Hossler 65-67
133 - Bubba Watson 70-63, Rory McIlroy (NIR) 64-69, Lanto Griffin 70-63
134 - Anirban Lahiri (IND) 67-67, J.B. Holmes 66-68, Ryan Blaum 69-65, David Lingmerth (SWE) 67-67, Jason Day (AUS) 66-68, Steve Marino 66-68