RealGM

Based on the rankings explanation provided by CBS regarding the NFL playoff situation; CBS provides something regarding a common record:

Seattle is ahead of Detroit based on common games record (4-0 to the Lions' 2-2).
What is a common games record? How does the NFL settle tiebreakers for teams that are being considered for the wild card?

What tiebreaker rules are considered when two teams have the same record?

http://www.nfl.com/standings/tiebreakingprocedures

common games would probably be their records against common opponents

packers
panthers
cardinals
giants

seahawks are 4-0 and lions are 3-1 vs the four teams they have both played

Because Detroit and Seattle are not in the same division, the 1st tie-breaker is conference record.