Dunfner strives for his first PGA Tour title

"I had a couple of easy birdies," Dufner said. "I don't think I missed a fairway or a green. Just had some tough reads. The greens are kind of tough to read. Sometimes you get competing grains, competing slopes, so you get a putt that might break to the right, but the grain is going left. That can be kind of difficult to judge. Then 18, I had just a really good number for my 5-wood to get somewhere on that green and had a putt that was down grain and breaking to the left with the grain, so that was a nice way to finish the day."

Greg Chalmers holed out for an eagle on the par-4 first and also finished with a 64 to join Steve Stricker and Ernie Els at 10 under. Stricker and Els shot 68.

Knox and Chalmers matched the course record.

Second-ranked Luke Donald rebounded Mizuno MP 53 Irons from an opening 73 with a 65 to reach 6 under. Donald, tied for 22nd, needs to finish sixth or better to regain the top spot in the world from Rory McIlroy.

Knox, a Nationwide Tour graduate playing in his ninth tournament, had seven birdies and an eagle — on No. 18 — along with one bogey.

"You never plan on shooting a 64, it kind of happens and I'm happy it did," Knox said. "I haven't played well this year so far, but it's been the best year of my life."

"I played really solid all the way through 11 and then missed that put and kind of lost my thought process there for a little bit," Stricker said. "Felt like I let a really good one slip away today."

Donald also holed out from the fairway on the first hole, marking the first two eagles on the hole since the tournament was first played at the course in 2005.

Stricker had four consecutive birdies beginning on the seventh to move into a tie with Dufner, then missed a 2-foot birdie putt on the 11th that would have given him sole possession of the lead. Stricker stumbled home with bogeys on the 12th and 15th.

Watson walked over toward Leonard, put on a new golf glove, signed it, then took it off and gave it to Leonard and shook his hand. Watson's caddie, Ted Scott, drew laughter when he instructively TaylorMade R11S Driver pointed farther down the fairway and said, "We're glad you're all right, but if you could just angle your head a little differently …"

Watson, away from his wife and recently adopted son after taking a two-week break following the Masters, eagled the seventh and birdied the eight, but bogeyed the 10th when he missed the green from 47 yards on his approach. He also three-putted the 12th for another bogey, moving him to 1 under, one above the cut line.

Watson's tee shot on the second hole at the TPC Louisiana drew blood from the back of Radd Leonard's head.

"I saw it coming and it looked like it was hooking right at me. I wanted to see that big hook, you know, and I got to see it. I turned and ducked and it still hit me," Leonard said. "It gave him a good discount golf clubs, anyway."

"Mentally, I've lost focus just about every shot, so I'm trying to figure it out," Watson said. "I want to be home with my son and wife. I know it sounds like a cop-out but I'm not playing very good because I'm just really not into it."