In McCarthy's own words, they arrived jacked-up, had extra time to heal and prepare, had a complete roster of healthy people. With an Aaron Rogers, on their best day, they can compete with anyone. Again, McCarthy more or less said they played their best game (the players no doubt felt the same way and that is why it was so devastating to lose the way they did). Although, I think it needs to be pointed out that the Rams were ahead at the time of the fumble, and to think that Rogers was going to automatically drive them into FG range, and that their FG kicker was going to automatically make the FG to win the game is a bit over the top.
By the end of the game it was the Rams who had the momentum, not GB.
The Rams are going to see many great efforts like this as every team wants to be the first to beat the Rams. Don't be looking for any more gimmies.