FRISCO, Texas -- Padraig Harrington didn't intend for the PGA Championship to be a tuneup for the senior version a week later.
It could be turning out that way.
Harrington shot 8-under 64 on Thursday in the first competitive round at the new Texas headquarters of the PGA of America for a two-shot lead at the Senior PGA Championship.
The 51-year-old Irishman finished 7 over at Oak Hill with an 8-over 43 on the front nine Saturday. Par instead on that wayward nine would have meant a top-20 finish, but Harrington didn't see it that way.
"I was at least a week short in preparation," Harrington said. "I felt I was getting into it last week, but I wasn't there. I need to do a better job when I'm away from tournaments. So, last week it definitely helped me get where I am today, no doubt about it."
Japan's Katsumasa Miyamoto shot 66 and Brazilian Adilson da Silva had a 67 in the Senior PGA debut for both. Phillip Price also shot 67 at PGA Frisco's Fields Ranch East course, about 35 miles north of Dallas.
Stewart Cink was in a large group another shot back in his first PGA Tour Champions start four days after turning 50. Miguel Angel Jimenez, Robert Karlsson, Thomas Bjorn, Alex Cejka, Charlie Wi and Richard Green joined Cink with 68s.
Steve Stricker, who won the season's first PGA Tour Champions major two weeks ago with his second consecutive Regions Tradition title, and defending champion Steven Alker shot 70.
Justin Leonard, seeking his first Champions title not far from where the 50-year-old grew up in Dallas, shot 71.
Harrington made a long birdie putt on the par-4 second hole and chipped in for another birdie at 10. He hit his approach to about two feet on the par-4 16th and got up and down from the fringe behind the green for birdie at the par-5 18th.
Playing partner Rocco Mediate, who was thrilled with his 69, said Harrington "dismantled" a course set to host the PGA Championship in 2027 and 2034, and possibly a Ryder Cup sometime in the late 2030s.
Harrington appreciated how Mediate was chatty during the round, the same he was with reporters afterward. ("So get to the 64 guy," Mediate said as he was finishing in the player interview tent with Harrington watching off to the side.)
"In some ways the reason it was an easy 64 is because when you're playing with somebody like Rocco, there's always a bit of chat and there's always a bit of fun going on, so you're quite relaxed," Harrington said. "There was just plenty of conversation. And you end up shooting 64 and you go, 'Oh, what, you know,' you'd nearly forgotten about your score."
Harrington won four times in his Champions debut last year, including the U.S. Senior Open and the season-ending Charles Schwab Cup Championship. He has four top 10s in five starts this season.
Starting on the back nine, Miyamoto opened with a 32 that included a bogey before getting two birdies on his back nine.
"I started with the birdie, birdie, birdie, so nice rhythm," Miyamoto said. "First tee shot very nervous, but make a birdie, so kind of relax. This course is really tough. The rough is tough."
There were two aces among the early finishers. Dave McNabb recorded his on the 161-yard eighth hole on the way to a 78 for the Pennsylvania club pro.
Corey Pavin had one at the 183-yard No. 4 when his shot bounced on the front edge of the green and rolled about 40 feet into the cup. The 1995 U.S. Open champion shot 71.
Cink eagled the par-5 first, his 10th hole of the day, with a second shot that settled inside five feet. His round included five birdies and three bogeys.
The 2009 British Open champ said he stays in touch with his contemporaries who had already moved on to the Champions circuit, but rarely gets to see them. Until now.
"I can see why guys really enjoy playing on the PGA Tour Champions. It's fun," Cink said. "And after you've been in the grind for a long time - it's a grind out here, too, the guys play great. But it's just, out here, it's like grinding with a smile."