Not sure why the Bruins would add an unproven kid with Vaakaneinen and Zboril having got their feet wet last year and both worthy of continued investment.
Not sure why the Bruins would add a middling talent at LD when they have Gryz, Reilly and Forbort at LD, all of whom are clear NHL defensemen.
They aren't going to trade Reilly or Forbort who they literally just signed.
That leaves looking for an upgrade on Gryz (with Gryz on the way out, likely).
The Grzelcyk/McAvoy pairing had a 64% Corsi, 68% SF, 74% GF, 66% xGF, 64% SCF, etc, etc.
Gryz/Carlo was in the high 50s for all those metrics.
I know some people are on the "PLAYOFFS ARE DIFFERENT! GRYZ SMALL! SMALL BAD!" bandwagon right now... but those are very very good results... and the results in the playoffs for Gryz/McAvoy were still high 50s on everything!
So basically, for the Bruins to add a LD, it has to be someone GOOD.