I mean you have to trust that these kids will develop as the season goes. The NHL is changing and getting younger. Remember Keith, Seabrook, Forsling, HJ, and Murphy will be here in some combination so it is not be like you think it will be.
Keith will continue to decline with age, as will Seabrook. So you can't expect them to carry the D like they used to.
You still need one of Jokijaru or Boqvist to be your top-pairing guy, as Murphy is somewhere between a 4/5.
Jokijaru is still young. He looks okay now through nine games, but are you sure he's going to be at a top-pairing level from here on out? I think it's a mistake to not prepare for him to go through stretches of miserable play as he continues to grow.
We still don't know exactly what we have in Forsling. We think we have a top-4 offensive defenseman, but we really don't know for sure.
Boqvist, Mitchell, and Beaudin
could come in and surprise, but it's reasonable to expect them to need more development time before becoming impact NHL defensemen.
I'm not saying it can't be fine, but I think it's a mistake to hinge your immediate future on the potential of these very young defensemen while your impact vets are hitting their declines.