BOSTON (CBS) — Four games into the Stanley Cup Final, the Boston blue line is starting to look like a black and blue line. The Bruins could be without both Zdeno Chara and Matt Grzelcyk for Thursday night’s Game 5 in Boston, which would cause head coach Bruce Cassidy to do some roster tinkering.

Grzelcyk is still on the mend and in the NHL’s concussion protocol after taking a big hit in Game 2. Cassidy hinted that Grzelcyk could return at some point in the Stanley Cup Final against the Blues, but only time will tell.

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Chara’s status is up in the air after the B’s captain took a puck to the face in Monday night’s Game 4 loss in St. Louis. He had to be stitched up and never re-entered the game, watching the final period of Boston’s 4-2 loss from the Bruins bench.

Cassidy didn’t have any update on his injured D-man Tuesday morning, but hopes that one will come later in the day when Chara and the Bruins return to Boston. He’s aware of the challenge the Bruins face if both of their injured defensemen can’t go on Thursday night, and said he may go with seven blue liners if that’s the case.

“This matchup is not good with Z out, let’s face it. They’re a big, heavy team, so we lose that element,” he said. “But someone else is going to have to step up, and I think we do it as a group.”

The two injuries have created holes on Boston’s top and third defensive pairings. John Moore took over for Grzelcyk in Games 3 and 4, averaging 17 minutes of ice time. Cassidy mentioned veteran Steven Kampfer and young defensemen Jakub Zboril, Urho Vaakanainen and Jeremy Lauzon as players who could join the defensive corps if Boston goes with a seven-man group. Kampfer has played in two games for the Bruins this postseason, while the other three have no playoff experience and just 20 regular season games among them.

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But adding a few more defensemen to the mix means the Bruins will only dress 11 forwards, so someone from that grouping would need to watch Game 5 from the ninth floor. With no points and just over 10 minutes of ice time over the first four games of the series, David Backes appears to be the prime candidate.

Going with seven defensemen would also affect Cassidy’s forward groupings, though the head coach said he’s already considering a shakeup to try to get Boston’s second line going. David Krejci does not have a point yet this series and Jake DeBrusk has gone six games without scoring a goal. There’s a chance that David Pastrnak could skate with that pair as they try to heat up with the series entering a critical phase.

“We’ve moved Pasta in there periodically for a few shifts here and there. We have to sit down with them and they have to change the way they’re playing,” Cassidy said of his second line. “It hasn’t worked so far to generate offense.”

Cassidy isn’t too concerned about any chemistry issues that could come from his shuffling. And he certainly isn’t going to let any of his players use that — or injuries — as an excuse with the Stanley Cup Final now down to a best-of-three.

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“What we shouldn’t be worried about is, ‘Can we win without certain guys in the lineup?’ We’ve done it,” said Cassidy. “There should be a mindset that we can still get it done.”