He flubbed a chip trying to be too perfect and missed a 4-foot bogey putt. Much like McIlroy, he responded in splendid fashion by closing out his round with four straight birdies, finishing with a 30-footer on the ninth hole.
Westwood also had a 65 in the third round at Congressional in the 2011 U.S. Open.
"I've played better rounds of golf, but I was really pleased today," he said. "I hit a lot of quality iron shots, and it felt like 65 was a fair enough score for the way I played. I got a couple of bad breaks out there, but I rolled a couple of putts in that you probably wouldn't expect to hole. But that's just the way it is. A bit of momentum is a wonderful thing."
The timing was great for Westwood, who is trying to avoid missing the Ryder Cup for the first time since 1995. European captain Paul McGinley told Westwood he wanted to see some form, and Westwood has delivered a 63 at Firestone and a 65 in the opening round of the final major.
Chappell played bogey-free in his 65, while a late bogey was about the only thing that spoiled Palmer's day. He was the only one to reach 7-under par, with a birdie on the seventh hole, and he allowed himself to think about two more birdies for a 62 and the lowest score ever in a major. He missed a short par putt on No. 8 and that was that.
"I wanted to get to 8 (under) so bad and it kept driving me," Palmer said. "So we'll take 6 going into tomorrow."
The course was generally soft and gentle, and it showed in the scores.
While it's daunting to see McIlroy anywhere near the lead the way he's playing, Valhalla offered good scores to plenty of players.
Henrik Stenson and Jim Furyk were among five players at 66. Kentucky native J.B. Holmes had a 68 despite taking a double bogey on the 13th hole when his drive landed in a divot and his next shot to the island green didn't find the island.
Phil Mickelson played alongside Woods and rallied for a 69.
For Woods, it was the second straight round in a major when he didn't beat the Ryder Cup captain, 64-year-old Tom Watson, who had a 1-over 72.
Watson was more interested in how his team was shaping up than his own game. Qualifying ends after the PGA Championship, and Watson gets three picks on Sept. 2.
"I'm going to with horses that are running well," he said.
After one day, Tiger was stumbling badly. Woods' first order of business Friday was simply to make the cut.