“Anytime you can set or equal a record in the Open Championship, it’s special,” Oosthuizen said.But what Oosthuizen truly craves at age 38 is a second major championship to go with the British Open he won at St. Andrews in 2010. Since then, he has been runner-up on six occasions, most recently at this year’s P.G.A. Championship and U.S. Open.“I’m sure after the last two majors he’s even more motivated,” said Spieth, the 27-year-old American who is chasing his fourth major title, and his first since winning the British Open in 2017.Established threats abound at Royal St. George’s. Dustin Johnson, the world No. 1, and Brooks Koepka, a former No. 1, both made moves on Friday. Johnson was at seven under par, four shots off the lead, after shooting a 65. Koepka was at five under after a 66. Phil Mickelson, with a two-round score of 152, missed the cut.“That’s a good leaderboard,” Oosthuizen said, sounding wary, and with good reason.Morikawa, like Spieth, bears close watching. He made two significant changes after the Scottish Open. He switched to new 7, 8 and 9 irons to improve his feel.“Those are three crucial clubs that are some of my favorite clubs,” he said. “My 8-iron is my favorite club in the bag, and when I wasn’t able to hit it last week, well I knew I had to try something different.”This week, he has also resumed putting with a conventional grip on longer putts. When he was struggling with his putting earlier this season, Morikawa consulted with Mark O’Meara, the 1998 British Open champion, and switched to a grip called “the saw,” which limits the influence of the right hand.