It starts with the defense (and I'll get to the Packers' offense later):
The last time the Packers opened the playoffs on the road (2010 season) it was against the NFC East champion (Eagles), and the Packers featured one of the best pass defenses (6th overall in 2015 according to Football Outsiders vs. 1st overall in 2010). But that's about where the similarity ends. The 2010 Eagles had a good pass offense and an elite rushing attack, while the 2015 Redskins can't run the ball to take advantage of the Packers' average run defense. Their late season winning streak (they won 5 of their last 6) has been because of QB Kirk Cousins, who's been very accurate (69.8 completion percentage on the season) and with only 1 INT in his last 6 games.The #Packers defense allowed just one touchdown drive & 242 total yards on Sunday. More: https://t.co/Acs2MVEkpj pic.twitter.com/micu5bvVTG— Green Bay Packers (@packers) January 4, 2016
And that's the knock on Cousins. Over his last 6 games, the Redskins have played a collection of mediocre to awful pass defenses. The last time they played a quality pass defense was mid-November against the Panthers, and they got clobbered by 28 points. Just as QB Aaron Rodgers has to play better for the Packers to make a playoff run, the Redskins won't win with a bad game from Cousins (the Redskins are 0-4 when he throws 2 INTs in a game this season).
Meanwhile, Cousins hasn't been relying heavily on any one receiver. TE Jordan Reed is his best, but the Packers are ranked No. 4 overall against TEs this season according to Football Outsiders. The Redskins do a number of good receivers (Garcon, Jackson, Crowder) but luckily the Packers have a lot of depth at cornerback to offset that advantage, especially if CB Sam Shields is recovered from his concussion this week.
The Packers defense matches up very well against the Redskins offense, which is why the Packers will beat them on Sunday.