If Dez Bryant plays... the Packers defense will have no answer. You have to stop:
1) Zeke Elliott, best in the NFL, on the ground
2) Cowboys elite short/intermediate game with Witten, Beasley, and screens to Elliott and Dunbar
3) Dez Bryant intermediate and deep -- must double
Packers have several options to counter, but it's largely "pick your poison".
7 in the box = allows you to double Dez Bryant and play coverage on the other receivers, but you get eaten alive in the running game by Zeke and the best OL in the NFL.
8 in the box = depending on the Cowboys formation, you may or may not be able to double Dez Bryant, but even if you can, Beasley and Witten will be open for easy 10-15 yard completions all game.
9 in the box = you're man on man throughout and while this will succeed in squelching the run game, you can't do this if the Cowboys go 3-wide, and the Cowboys will be going deep often, particularly to Dez.
Plus, you have to account for all the wrinkles/play action QB runs and bootlegs with Dak Prescott as he's always a threat to pick up a first down on the ground if you don't account for him. With Romo on the field you can eliminate this threat as a defense, though Romo is arguably the most savvy in the league at avoiding the sack and finding his deep target.
Packers defense is really in for it here... yes they're ranked #1 in rushing defense but that's the absolute definition of fool's gold because their 4 opponents so far are ranked 30th, 32nd, 23rd, and 27th, respectively in rushing offense. The Cowboys are ranked #1 in rushing, Tennessee is a jump below at #2 with Murray... after that, it's a pretty big dropoff.
Cowboys 31-24.
That being said, if Dez can't go I may change my pick to GB before the game. It's a huge factor on offense.