Here are the potential 3-way ties at 10-6 with Seattle:
Carolina & Seattle - Conference record eliminates Carolina, Detroit wins common games over Seattle
New Orleans & Seattle - Same as Carolina
Atlanta & Seattle - Atlanta wins head-to-head sweep
Seattle going 10-6 greatly helps the Lions chances, as long as Atlanta is not involved
The last one is the one that probably keeps them out. The first two probably don't happen.