Replacement level is completely subjective by team. Danny Espinosa is a 3-4 win player over a theoretical player that we could call up from AAA. He is not a 3-4 win player over Nats replacement level, since Lombardozzi is probably a 2-win player and would be his replacement.
Here's my list of worst injury replacements on the Nats:
Zimmerman to Chad Tracy
Strasburg to 6th SP
Gio to 6th SP
Harper to Moore
Zimmermann to 6th SP
Desmond to Lombardozzi (Espinosa stays in the lineup at SS and Lombardozzi replaces Desmond in lineup)