Is he the sole reason? No. Is he part of a lineup that hasn't played together showing little chemistry, terrible defense and suspect goaltending. Yes.
Casey isn't to blame but he hasn't helped much either. I delved into this subject on Rakish's podcast if anyone wants to listen. They we're winning with Eric Cornel, Dalton Smith and Nathan Paetsch contributing.
They just need a few games/practices together to get reacclimated with everyone. Here is a nice tidbit: