The Cowboys defense was decimated by injuries last year.
I think they had 5 or 6 starters on IR at one point and Ware was playing with one arm by the end of the season. If they are even somewhat healthy (especially Sean Lee and Bruce Carter, they are key vs RG3 and Morris) the defense should have a big turnaround - the last time the Cowboys made/won a playoff game was 2009 which was the last time the Cowboys had an above average defense and a positive turnover margin. It was also Romo's best season turnover wise because he wasn't having to put every game on his shoulders and he could be more cautious because he could trust his defense wouldn't give up the lead every game. (See Cowboys 2011 and 2012 seasons, especially in December)
I think they had 5 or 6 starters on IR at one point and Ware was playing with one arm by the end of the season. If they are even somewhat healthy (especially Sean Lee and Bruce Carter, they are key vs RG3 and Morris) the defense should have a big turnaround - the last time the Cowboys made/won a playoff game was 2009 which was the last time the Cowboys had an above average defense and a positive turnover margin. It was also Romo's best season turnover wise because he wasn't having to put every game on his shoulders and he could be more cautious because he could trust his defense wouldn't give up the lead every game. (See Cowboys 2011 and 2012 seasons, especially in December)