Cassidy did not completely rule out Patrice Bergeron (lower-body) returning against Arizona, but said that it "doesn't look like he'll be in."
Bergeron did not participate in practice on Friday, but did come out at the end of the session for some work, as he has for the last several days.
"He's out there skating. That's a good sign," said Cassidy. "Obviously without being able to participate in practice you're always concerned that you need one of those good practices before you play, but he'll be updated tomorrow.
"He could get up in the morning, come and skate and pronounce himself ready. A guy like him will get the benefit of the doubt, but generally I think that's a stretch without having one good practice."
Cassidy did not sugarcoat the adverse impact Bergeron's absence has had, but also did not want to use it as an excuse for the team's back-to-back losses.
"It hurts. He's arguably our best player night in, night out. He makes people around him better. We use him in all situations. But we need to find someone else. It's that simple," said Cassidy.
"I'll do that tonight with my wife on the phone, I'll complain about missing him. But right now, it's next man up. I know it sounds simple, but we've got other guys in that locker room that have to get hungry and respond to the challenge…we got some of it the other night, we just need more."