In his first major stumble of the tournament, Dufner drove his ball into the water at the fifth hole and wound up with a double bogey. He got one shot back, rolling in a 12-foot birdie putt at the seventh, but missed a short putt at the eighth for a bogey.
Furyk made the turn tied for the lead at 7 under and seized it outright with a birdie at the 10th, pushing his score to 1 under for the day and 8 under overall. But Dufner came along a few minutes later and rolled in a 15-footer of his own, reclaiming a share of the top spot.
Henrik Stenson, Adam Scott and Jonas Blixt were two shots back.
Blixt was the leader in the clubhouse, shooting a 4-under 66 that left the Swede at 6-under 204 heading to the final round.
David Hearn of Brantford, Ont., briefly the clubhouse leader during round 1, fell to 3 over for the tournament after carding 1-over 71 Saturday. Hearn looked like he was going to turn in a strong round, but he followed a bogey on 17 with a double-bogey on 18.
Dufner was coming off a 7-under 63 on Friday, tying the major championship scoring record. In fact, 27 players were under par after 36 holes — on a course that doesn't give up many red numbers.
But low scores were hard to come by on a warm, sunny day in western New York. With the leaders all past the turn, Furyk was the only player in the final five groups below par for the round.
With so many players faltering, defending PGA champion Rory McIlroy charged up the leaderboard. The 24-year-old birdied the last two holes — among the toughest on the course — for a 67 that pushed his score to 3-under 207. He chipped in at the 18th, pumping his fist as he went to retrieve his ball.
Over his last 25 holes going back to Friday, when it looked for a while as if he might miss the cut, McIlroy is 7 under with only one bogey.
After a season-long slump that included missing the cut at the British Open, he suddenly looks more like the player who romped to a record eight-stroke victory at Kiawah Island last year, earning his second major championship.
"It's getting there," McIlroy said. "It was good to feel that sort of rush again."
Phil Mickelson and Tiger Woods headed in the wrong direction.
Mickelson, who won at Muirfield just three weeks ago, was next-to-last among the 75 players making the cut after an ugly 78 left him at 10-over 220. Lefty had a triple bogey at the seventh, then a double-bogey at the 14th when he chipped through the green twice before finally getting one to stick.
He stalked off the course without speaking to reporters.
Coming off a seven-stroke victory at the Bridgestone, Woods turned in another mediocre round (73) that ensured another year without a major title. He was at 4-over 214 and a staggering 13 shots behind Dufner before the 36-hole leader even teed off.
Woods will go to 0 for 18 in the majors since his last win at the 2008 U.S. Open.
"Well," he said, "it was hard to me. I didn't played very well today. I didn't hit it very good, didn't make anything, kept blocking every putt. So it was a tough day."
While the wind picked up and the course played much tougher than the first two days, there were still chances to go low. Dustin Johnson shot a 65. Kevin Streelman signed for a 66.
"I played really well," Johnson said. "Drove it well, drove it in the fairway, made some good putts."
For Dufner, the weekend provided a chance to shake off the low point of his pro career, when he squandered a four-stroke lead with four holes to play at the 2011 PGA in Atlanta.
After losing to Keegan Bradley in a playoff, Dufner didn't seem too upset. He said matter-of-factly that he expected to get more chances on the major stage.
"What's happened in the past with me in majors is in the past," Dufner said Friday. "I'm still trying to chase it, still trying to learn from the mistakes I made in prior majors."
Dufner's popularity has grown since April, when someone took a photo of him during a charity event at an elementary school — slumped against a classroom wall, gazing straight ahead with a blank stare, arms rigidly by his side.
That sparked a craze known as "Dufnering," which seems to fit perfectly with his laid-back approach.
He showed about as much emotion as one will ever see after finding his ball in the water at the fifth.
Dufner angrily shook the head cover off his driver to mark his drop, then slammed the club back into the bag when he was done.
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