In recent years, the NFL has modified and relaxed some of its rules on roster limits and injury designations, and teams like the Cowboys have benefited from them when it comes to making the tough decisions. The expanded practice squad limit, for example, has made a big difference in how teams stack their depth.
Equally impactful is the advent of allowing players to return from the injured reserve after just four weeks, as opposed to eight weeks. At times, this has allowed the Cowboys (and plenty of other teams) to more easily absorb a longer-term injury by creating a roster spot to replace them without having to lose that player for half the season.