It was quiet in the visitors dressing room in Ottawa last Tuesday. Oh, there was the usual low din of ripping tape, clattering sticks, and jostling equipment. But there was something missing: The booming voice of Brent Seabrook and the usual pregame platitudes that tend to spill out of him like an unconscious tic in the moments before a game. “Let’s go, White! Here we go, boys! Come on, now!” “It was weird,” Connor Murphy said. “Seabs is one of those guys that’ll be yelling stuff in the room before a game in a good way to try to brighten the mood and get it going. It’s a little weird when you don’t hear that.” Joel Quenneville’s decision to make Seabrook a healthy scratch in Ottawa was a watershed moment for the Blackhawks. The venerable veteran is no longer untouchable, no longer above reproach. His play wasn’t good enough, and he was benched for it. Like he was just any other player. At 32 years old, with more hard miles behind him than most — since his rookie season of 2005-06, only Patrick Marleau and Joe Thornton have played more games than Seabrook (1,090 regular season and playoffs) — Seabrook is on the back half of his illustrious career. And he was never all that fast to begin with. He’s been burned a few times by younger, faster players. He’s been caught out of position a little too often. And he only has two goals. He’s been at his best when he’s playing third-pairing minutes, as he did in Friday’s victory over the speedy Winnipeg Jets. And he’s got six and a half years left on a contract that carries a $6.875-million cap hit.