Dufner wasn't as fortunate with his wayward drive, which settled under a tree. He had to punch a low shot around the branches before hitting his approach into a greenside bunker and two-putting from 23 feet for bogey.
But Dufner needed only one hole to get even again, with an 8-foot birdie at No. 12. Johnson hit his tee shot into a fairway bunker, then his first attempt out of there hit the lip and rebounded over and behind him before a bogey.
They were tied at 14 under going to the back nine after Dufner's double bogey at the 386-yard ninth hole, where his approach from 103 yards hit just short of the green and rolled back into the water.
After driving into a fairway bunker at the 382-yard second hole, Dufner three-putted from 28 feet for his first bogey on any of the first eight holes all week. Johnson made a 28-foot birdie putt to go in front by a stroke.
At No. 5, Dufner made an 8-footer for his third birdie of the week at the tight par 4 parallel to the Trinity River that is one of Colonial's toughest holes. Even after a frustrating tee shot into the rough at the sixth hole, Dufner regained the lead by rolling in a 34-foot birdie putt.
Johnson trailed by two strokes when his tee shot at the 188-yard eighth was way left before his short pitch shot missed the green and he bogeyed.
"What (Dufner) has done the last month is beyond impressive," Johnson said. "I kind of feel like I somewhat unseated a king to me because he has been on top for four weeks."
Divots: Hunter Mahan, No. 2 in the FedEx Cup standings behind Dufner, had three consecutive bogeys on the back nine and his only birdie in his round of 74 came on the last hole. He finished with a 282 total. ... Rickie Fowler, who in his previous two starts got his first PGA Tour win along with a runner-up finish at The Players Championship, shot a 69 and was in a group of five players tied for fifth at 275.
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