Murray was a good player for us and always a likable guy, but Richardson is the bigger loss. The woes with our interior run defense were real, but how much was Richardson and how much was Joseph being hurt is up for debate. What is being underestimated right now is Richardson's ability to generate quick pressure up the middle. There definitely some games that stood out more than other, but in a league where teams are increasingly spreading the field and getting rid of the ball quickly, then the quickest way to the QB is up the middle, which also creates opportunities for the pass rushers on the edge. I know that Stephen isn't the same caliber of interior pass rusher and what Jaleel Johnson and Jalyn Holmes are capable of is still a bit of an unknown. I would not be shocked if the Vikings look for an interior pass rusher early in the draft.
As for replacing Murray. That is probably more of a 3rd-5th round priority. Cook was finally healthy and looking better, but with Roc Thomas messing up his career & Cook's propensity to be banged up so far, the Vikings would be wise to have a good backup in place. That player should also be more of a power back like Murray was, though I'm not sure the type of back we add will be more of a 1-cut runner that fits Kubiak's version of zone blocking.