Just so we are clear on this (pet peeve of mine).
There are 3 types of strains - I, II, III. A grade I strain can imply that there are some torn muscle fibers (but mostly just stretched/slightly torn), grade II partially torn and grade 3 the belly of the muscle is torn completely. ESPN's report is redundant by saying "Rodgers has a partially torn calf in addition to the strain." It's a Grade II strain at worst. If it were Grade III, he wouldn't be able to walk.
Just my 2 cents - I hate seeing everyone overreact by this. It's not any worse than initially thought and with the off-week he'll be more healed up. The only silver lining of this news, because it has been blown out of proportion, is that he will be playing in the cold.
I liken him playing in the cold to trying to stretch frozen taffy or a frozen rubber band. It all depends how much he warms up and how much medication he takes to get the inflammation down.