They can be core pieces, I guess. Norris is paid like one, his durability will determine his worth. Kesselring is their 4th best Dman so that is on the edge of “core”. I think he will elevate Power’s progress so there is that.
If Norris plays 65+ games, that will be better than 82 Cozens games. He was brought in to be a part of the core. Kesselring is a hope to become a part of the core.
Winning teams have a core of stars that they roll out (Bobrovsky, Barkov, Reinhart) ( Vasilevskiy, Hedman, Kucherov, Point) but they also have some “core” role players.