Well Rust is smallish, predicated on speed. Sure he has tenacity. But the Pens just had too many guys of this size. I do think when they signed Rust, they should have then traded Jake, and gotten some bigger dudes.
The whole thing though, Rust, Sid, Geno, Letang, Jake, etc.....is not just they were getting older and to a varying degree, lessoning of their skills, but they were/are getting stale. The messages stale. This includes coaching. It seems like they don't hold each other accountable. They miss big personalities like a Dupuis, a Talbot, a Guerin and a Robert, an Orpik, this group just seems to lack the "heat" and passion to get on things when things aren't right.
Karlson is a talent, but he certainly is not a warrior type. And changing the bottom 6 is essentially rearranging the deck chairs on the Titanic, with this group. The big problem is the talent that has led this team to 16 straight playoff years are on the back nine, and some very back nine.