Poorly.
But there's a reason they are the starters. What valid reason would a coach have to put in the backups in a game that isn't over? If the backups were going to do better, why didn't they start?
We have a full week and goodness knows how many months of offseason to prepare for this and come to the conclusion that the backups will miraculously play better than the offense? Or that placing the backups in the game and then calling run plays and short passes will bring us back into it?
Somewhere along the line there is coaching that - if we're being honest and accountable - can be improved.