Well it's nothing close to Cup run d-core. Too many weak points, too many which need to sheltered.
There is currently 3 dmen who can defend. Parayko, Scandella and Bortuzzo. I don't count Gunnar, 'cus he's questionmatk will he be healthy again? And I don't count Mikkola, 'cus God knows what he needs to done get icetime at Blues Jersey. He has been already NHL ready dmen for 1-year. Hope he'll get opportunity or trade him for prospect forward.
And it's crazy that I have to include Bortuzzo too, only tells how slim our d-core is. This team was built strong defensive system and it get it for us Stanley Cup. Not type of players like Faulk who needs to babysitter. Dunn goes same category,but at least he can improve/develope his game compare to Faulk. Dunn has years left, Faulk is what he's.
Krug is question mark, but he lived fully behind the one of the best NHL line, Marchand - Bergeron - Pastrnak. You can be limited by defensively behind those guys. We don't have that good 1st line like Boston.
You have to be pretty blindfolded if you think our d-core is anything close what it was.
It's not atrocious, but it isnt anything near as top10. Close to 15-20 range now or worse.
So
Krug parayko
Scandella faulk
Dunn bortuzzo
Mikola reinke gunner peronovich
Yes our defense has gotten worse, but we pretty much had one of the best defenses in the league. So the only place to go was down. Losing petro was a hit. We now have balance and I think with Faulk on his natural side you will see his game improve. In no way is this defense atrocious