The Cowboys currently have three projected starters Sunday, Phil Costa at center, Bill Nagy at left guard, and Tyron Smith at right tackle with one combined career start (although a Costa knee injury might find Nagy sliding to center and recently signed Derrick Dockery in the lineup). Smith was a highly regarded prospect. Nagy is an undrafted second year player. Nagy is a rookie seventh round pick. Some low picks are ready quickly like Matt Slauson, but having a pair of guys this young who were not so highly regarded is risky. This is a line inexperienced both in terms of games played and games played together.
Why is this important? The Jets run an attacking style of defense. They blitz heavily. The blitzes are successful for two reasons. The first is they frequently send more rushers than the other team has blockers in a given area. The second is the exotic angles from which the Jets blitz cause confusion and lead to blown assignments. Protection fails to identify and slide to adjust for a rusher. Having experience working with the guy next to you can be very helpful. After spending time with your fellow linemen, you learn how everybody reacts to certain situations and can adjust accordingly. You may have seen something similar in the past and already know how to respond. It can make all the difference in the world when a blitzer forces you to adjust in less than one second, and there is no time to communicate. The opposite is true for new lines looking to gel. A lack of cohesion is a disadvantage.
Considering how young Dallas will be up front, it is likely the guys there will have never seen anything like the looks are going to throw at them, let alone be able to work out how they will work in unison to respond.