Being the OC of a team for 3 years gives a coach an advantage taking over as HC because they know the team and the players. It should provide a smooth transition which is why some teams hire within house when looking for a new HC. Garrett being with the team and having 8 games to get his feet wet at HC in 2010 gave him a huge advantage over Jim Harbaugh who was coaching at Stanford and took over the 49ers during a lockout. If you knew after Garrett finished 5-3 in 2010 that he would only win 8 games the next 2 seasons would you have been on board with him taking over as HC? Have you seen progress in the Cowboys since he took over? If so where do you notice the progress? By the way you still haven't answered the question about the defense.