You're pretty much screwed the game the injury occurs in, especially as early in the game as this one occurred.
The problem is that with limited time, limited repetitions available during the week, you focus on the main game plan. That means the starter (Rodgers) gets the repetitions. Even if you've got a good plan if the starter goes down, the backup gets few repetitions, the receivers get few repetitions with the backup, etc.
If you haven't practiced it during the week, it's extremely difficult to execute it well during the game.
This next game will be a better indication of what to expect, after they have an opportunity to tailor the game plan to Hundley (and more importantly, practice that game plan).
When Rodgers went out and Flynn played the next week against NE, we came very close to winning. It was stupid stuff like letting a lineman lumber down the field to the goal line on a KO return that lost us that game, not Flynn.