Higgins is supposedly more defensively responsible than Kassian, and with a very young and patch-worked defense filling-in for the regulars,...that matters. Kassian is still a crap-shoot and an adventure. It's about where WD can place his trust.
Sometimes I think other than with face-offs, Higgins can play the game like a centre, and become quite the set-up man. Just looks at his assist totals. Is Vey really all that, too,...& more?