PINEHURST, N.C. — Colin Prater feels a little like Kevin Costner’s character in “Tin Cup” this week — a relative unknown who suddenly finds himself thrust onto one of golf’s biggest stages at the U.S. Open. It’s a movie Prater is quite familiar with, which is why he and his caddie staked out a spot at the far right end of the practice range — just in case things went completely awry. “It was funny we were joking before we got out here, like, we’re not going to the left side of the range just because we didn’t want that dreaded S-word to kick in,” Prater said with a laugh, referring to Costner’s character who developed a case of the shanks before his round.