Spraying shots all over Valhalla, Tiger Woods made four bogeys, managed only one birdie and finished with a 3-over 74 that left him nine shots off the lead in 109th place after the opening round Thursday.
Westwood matched his best round ever at a major, making nine birdies as he carried over the momentum from a closing 63 at Firestone. The 41-year-old Englishman also had a double-bogey on his 10th hole of day -- at No. 1, after starting on the back -- but closed with four straight birdies.
"The golf course was all there in front of me. I just play it as I see it," said Westwood, who has had numerous close calls but never has won a major championship. "Last week, I felt like I turned a corner."
Chappell, a 28-year-old Californian in his fourth year on the PGA Tour, turned in a bogey-free round. The final major of the year has produced some unlikely champions, and Chappell hopes to be the latest.
"I can't complain about being in the lead of any golf tournament," said Chappell, whose only professional win came on the Web.com Tour in 2010. "I just look forward to keeping it rolling."
Chappell was surprised to get an invitation a week ago Monday. He was at No. 104 in the world, not eligible in any category. Turns out the PGA Championship thought he was close enough to the top 100 to merit an invitation.
The UCLA grad took it from there. He hit an 8-iron to 6 feet for birdie on the 496-yard second hole. He also holed a bunker shot.
Palmer birdied five of the nine holes on the back side, which is where he started his round. He said the greens were more inviting than he expected.
"I was surprised how soft they were," he said. "It was a pretty easy, relaxing nine for me."
McIlroy admitted he was none too pleased after he snapped his second shot at the par-5 10th hole out of bounds, leading to a double-bogey 7 and a temporary state of annoyance during which he three-putted on No. 11 for another dropped shot.
He responded, however with four consecutive birdies and added another at No. 18 to trail the leaders by just a stroke.
"I'm really happy with everything," McIlroy said. "I've got a good thing going right now. I'm trying to ride that momentum as much as I can."
Furyk is off to another strong start in a tournament he nearly won in 2013.
He took a lead to the final day at Oak Hill, only to lose to Jason Dufner by two strokes.
Dufner's title defense lasted only 10 holes. Plagued by a sore neck, he withdrew after a triple-bogey left his score at 8 over, probably ending his Ryder Cup hopes as well. He came in ranked No. 8 in the standings and hoping to somehow play well enough to stay in one of the nine qualifying spots.
"I tried to do what I could to be able to compete some and give it a go," Dufner said, "but it is just pointless."
Phil Mickelson, mired in his longest winless streak since 2003, was paired with Woods for one of the rare times at a major. Lefty was 1 over midway through his round, struggling just like his playing partner, but fought back on the second nine for a 69.
Woods yanked one shot into the gallery, put another into a creek. He looked very much like someone playing just his 11th competitive round since back surgery March 31.
Woods arrived at Valhalla only on Wednesday after treatment for a back injury that forced him to withdraw from Firestone last week.