Grass damaged by cottontails:

If you see irregularly shaped dry/yellow grass spots by your home, chances are it's not a lack of water or a disease but cottontails. Cottontails are territorial -  once they get to like a spot they keep coming back to it.

Inspect the dry patch: if you see small round black droppings, especially when the soil underneath is wet, it's a sure sign the damage is caused by cottontails.

There is no known solution to the problem (other than breeding coyotes 😉), and if you replace the dry grass patch there is no guarantee that the cottontails won't come back to the same spot.