Gibbs answered questions about that in his press conference today--lots of injuries was one reason (at least 10 players), and both the full coaching staff and the team captains and vets felt like it was the right move. Take a break, recharge, and get back to work with a vengeance.
As Gibbs said, anything can be second-guessed, and this will be too if they lose to Detroit. But if they win, no one will compliment Gibbs on making the right move!
Washington Redskins