DETROIT — Michael Rasmussen arrived in Detroit just in time to watch the Stanley Cup playoffs, not play in them. But after years of wondering what that experience might feel like, the Red Wings’ second-longest-tenured player —only Dylan Larkin has more seniority here — is eager to find out for himself later this spring. “I think about it all the time,” the 24-year-old Rasmussen said after practice Wednesday, less than 24 hours after signing a contract extension to remain in Detroit for another four years. “I watch playoff hockey every time that we’re not in it, and I’m pretty jealous. It looks…