Cowboys and Eagles play next week. One of them will finish with a better record than us and Atlanta already has clinched with 10 wins, we can only get 9.
This is why the Atlanta win eliminated the Redskins despite their victory over the Eagles yesterday.
It meant that there was only one WC slot left (either Carolina or Atlanta will have the other slot at 10 or 11 wins).
Since they play each other the worst that the better team out of Dallas and the Eagles can finish is 9-6-1 and 9-5-2 (if they tie), meaning no 9-7 team can make it.