"It was a bit of a curveball. Leading into today, we thought he'd be cleared. But doctors felt otherwise, so we'll look at Saturday now," said Cassidy. "It's business as usual once the puck drops, an opportunity for someone else."
With Bergeron still sidelined, Jack Studnicka will once again get that opportunity as he plays the middle between Brad Marchand and Jake DeBrusk on Boston's top line.
"I think Jack has been good in terms of his 200-foot game," said Cassidy. "Has played well away from the puck. The offense should come if that continues. He's with two good players. It's a good opportunity now for him against a two-time defending Stanley Cup champion. That's the way we look at it.
"Other guys will pick up the slack. We've seen that with [Charlie] Coyle, [Erik] Haula the other night. It's been good for the other guys in the room to have that opportunity. That's the positive, the flip side of it. We'll keep on trucking here."
Even without Bergeron, the Bruins will be focused on gaining more ground on the Lightning. Now just one point back of Tampa in the Atlantic Division standings, the B's can jump their rivals with a victory and tie Toronto for second place with 85 points.
"I think we both understand what this game means and how important the points are," said Marchand. "They're just a competitive team. They always bring their best. They're always hard to play against. And we've been on top of our game. Every game seems to ramp up a little bit more this time of year.
"Guys are more focused or they're more dialed in their system. So, it'll be a good game. It'll be a hard game to play, but they're always the most fun to be part of."