If Guzman sits, the Nats have to commit an extra $400 K to SS so they can pay Ian Desmond.
If Guzman plays, they have to commit an extra $400k to replace his bench role. Either way, Guzman gets paid, and 24 other guys get paid. Only if they release him do they actually have to fill another roster slot, and we're only talking $400k, so let's not get too carried away with the financial angle. It's as minimal as it gets.