First thing I want to say is this: If the Dallas Cowboys fired defensive coordinator Rob Ryan because they wanted to switch from a 3-4 defense to a 4-3 defense and they don't already have Ryan's successor lined up, I think they're nuts. I don't think you decide as an organization to switch to a 4-3 and then decide you're just going to go out and hire the best 4-3 guy you can find to run it. Not all 4-3s are created equal, and I think the better way is to find the coordinator you like and involve him in the process of making the switch, right from the start. So my first thought here is that, if the head coach and/or owner have decided to make this switch, Cowboys fans should hope they've already been in touch with whoever's going to be in charge of actually implementing it.
But you know, there were performance-based reasons to fire Ryan if that's what they wanted to do, and obviously teams don't always operate with common sense as their guiding principle, so it's possible that Jerry Jones and/or Jason Garrett have decided to go to a 4-3 without thinking it through to that extent. I actually think it's possible that they're doing it for economic reasons. John Clayton has the Cowboys projected $18.2 million over the salary cap, which means there are a lot of people on the current defense who don't fit into the budget. Switching to a 4-3 could help that.
Think about it. If they can't afford to keep Anthony Spencer, Jay Ratliff and Marcus Spears, they could move to a 4-3 alignment with DeMarcus Ware and Tyrone Crawford at the ends and Jason Hatcher and Sean Lissemore at tackle. Sean Lee plays the middle linebacker, Bruce Carter the weak side and you go out and find yourself a strongside linebacker, which would be easier and cheaper than keeping or trying to replace Spencer as a 3-4 outside linebacker. Crawford, last year's third-round draft pick, is probably better suited to be a 4-3 end anyway, and the price is right on him.
Financial reasons might not be the most sound or inspirational motivation behind a change like this, but they are a facts of life, and I suspect they're at play in this decision here. I have little doubt that Ware could handle rushing from a three-point stance or that Lee would be an excellent middle linebacker. And if they were able to keep, say, Ratliff, he might benefit from being one of two 4-3 defensive tackles instead of a single 3-4 nose. So you can make this make sense in your head, which is what the Cowboys may be doing. I just feel like they need to figure out who's in charge of the thing before they start making offseason decisions based on some significant new framework.