Moore, meanwhile, is day-to-day with a lower-body injury of his own and could miss both ends of this weekend's back-to-back with the Stars and Arizona Coyotes.
"Had a little bit of aggravation during the game on Wednesday and it wasn't very good yesterday," said Cassidy. "Better today, but he's questionable for tomorrow's game."
So for those of you keeping score at home, here is the updated list of Boston's dwindling defense.
So, coach, ever seen anything quite like this?
"No. Not this many at the same time," said Cassidy. "Clearly when you lose guys through the course of the year, five or six, but not at the same time. It will be a challenge, no doubt."
The Bruins have turned to Providence for reinforcements, recalling Jakub Zboril and Connor Clifton, both of whom will make their NHL debuts against the Stars.
"It's the National Hockey League, you can either play in it or you can't. We'll find out with some of these guys," said Cassidy. "Sometimes this is the best way to find out, that's the positive in it. The negative is we've got a lot of good players out of the lineup back there.
"If they want to play here it's a great opportunity to show what they can do right now. That's the way I look at it. This is kind of their dream to get here. Well, here you are, have at it."
Zboril, the 13th overall pick in the 2015 NHL Entry Draft, has been working on adding a level of urgency to his game during his year-plus in Providence, and the 21-year-old Czech native hopes his progress translates to the ice tonight in Dallas.
"I've been waiting for this moment all my life," said Zboril. "Growing up as a kid, I was just dreaming of being in NHL one day and its' finally happening. Now I have like five hours to actually step on the ice and play my first NHL game and my feeling can't even describe it."