Losing a third-pairing defenseman doesn’t always seem like overly significant, but filling the void Matt Grzelcyk will be leaving is no easy task.

The Boston Bruins blueliner will be out, at the very least, for Game 3 of the Stanley Cup Final due to a concussion suffered in Game 2 from a hit by St. Louis Blues center Oskar Sundqvist. Grzelcyk is the best Bruins defenseman at defensive zone breakouts, and he’s done nicely to grow into the role of the second power play unit’s quarterback.

Bruins head coach Bruce Cassidy indicated Saturday morning that John Moore would replace Grzelcyk on the left side of the third pairing with Connor Clifton. Steven Kampfer was the other logical choice, but speculation about Urho Vaakanainen possibly playing grew after the 20-year-old skated on an extra pairing with Kampfer in practice Friday.

In terms of pure skating ability, Moore is the best skater on the Bruins’ blue line, but he’s struggled to stay in the lineup consistently. However, he’s a responsible player, and if for some reason he needs to start logging heavy minutes, he seems to be the one Cassidy would trust the most of the three.

So, why did Cassidy decide to go with Moore? He explained Saturday.

“Basically (deciding between) two guys that have been with us, Kampfer and Moore,” Cassidy said, via team-provided audio. “John’s a good player for us. He gets back on pucks, good size, real good skater. Kampfer’s done well when he’s been in there too, but Johnny’s a left stick, so is Grizz, so the left-right I think helps with balancing Clifton. Could’ve went either way to be honest with you, but we’re going this way and hopefully it works out for us.”

Puck drop for Game 3 is set for 8 p.m. ET at Enterprise Center in St. Louis.

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