When you think of the Dallas Cowboys' biggest rivals, the same teams come to mind. The Eagles, Giants, Redskins, and maybe the 49ers or Steelers based on your age.
Those are the teams which the Cowboys' success (or failure) against has defined both of their respective seasons. Beat those teams and you were successful. Fall short against those teams and it was often a wasted and disappointing year.
The past 10-15 years, however, two teams have very much entered that rivalry equation: the Packers and the Seahawks.
You cannot tell the story of the 21st century Dallas Cowboys without those two teams. Both have delivered debilitating losses to the Cowboys over the last decade, and the Cowboys have returned the favor against those two teams as well. And while most fans would quickly identify Aaron Rodgers as a clear thorn in the Cowboys' side, Russell Wilson and the Seahawks have just as strong an argument to be most-hated in Dallas.
Of course there was the Tony Romo game in 2006, where a dropped snap cost the Cowboys a playoff game and cost Tony Romo his reputation among the national media. But recent history has provided some gut wrenching moments as well, such as Romo's career ending back injury at the hands of Cliff Avril and the Dez Bryant era all but ending as Seattle dominated the Cowboys in 2017. Then there was the Earl Thomas drama, which nearly brought the All Pro safety from Seattle to Dallas before he suffered a season ending injury. 
These teams play just about every year, and each time seems to carry some franchise-changing implications to it. This Saturday is no different, with Seattle traveling to face the Cowboys in a Wildcard match up.
Jason Garrett has been defined by his lack of playoff success, as has the Cowboys franchise since the mid-1990's. Seattle, on the other hand, was thought to be closing in on the end of a dominant era, but are now hoping to ride their quarterback and running game to one final magical postseason run. Considering the next round's opponent, it's hard to picture either of these teams getting much further in the NFC playoff picture.
But given how their games tend to shake out, and the history altering results we normally see, I wouldn't be surprised if a win this weekend sparks a playoff run through the conference for one of these two teams.
