The hockey experts got this one right. Man, did they ever. They said this Bruins-Rangers Eastern Conference semifinal was going to be one of those nail-biting, could-go-either-way, intangibles-on-parade extravaganzas — and that’s exactly what you got for your dough, hockey fans. What, you were expecting a Red Sox-Yankees slugfest? It ended in overtime, of course, and it ended with the Bruins emerging with a 3-2 victory in Game 1 last night at the Garden, Brad Marchand doing the honors when he converted a feed from Patrice Bergeron. But before we get to the game-winning goal, let’s get to those intangibles . . . Such as how Marchand was doubled over in pain during the morning skate yesterday at the Garden, resulting in some concern he wouldn’t play. He played; he won it. Such as how the Bruins didn’t so much have a problem beating stellar Rangers goaltender Henrik Lundqvist as they had with beating the posts and crossbars behind Hammerin’ Hank. Consider that Johnny Boychuk hit a post, that David Krejci hit a crossbar, that Gregory Campbell tipped a Boychuk shot off the post, and that Jaromir Jagr hit a crossbar, and . . . hey, wait a minute: What happens when teams keep hitting the posts and crossbar in overtime? They lose, right? It’s practically a National Hockey League rule, is it not? “Yeah, that’s usually how it goes in the playoffs,” said Marchand. “One team does very well in overtime and then the other team gets a lucky one. We hit so many posts and had so many opportunities that (the Rangers) were bound to get one.” Such as how the Bruins, with defensemen Dennis Seidenberg, Andrew Ference and Wade Redden all idled with injuries, dressed three — count ’em, three! — rookie defensemen for Game 1 in Dougie Hamilton, Matt Bartkowski and fresh-from-the-minors, 22-year-old Torey Krug.