Jerry Jones recently echoed what we have heard since May: that NT Tank Johnson is the most improved returning Cowboy since the end of last season. The defensive staff quietly, then openly, raved about Johnson’s improvement following a so-so half season after arriving from Chicago. Johnson might not be a classic fit on the nose in a 3-4, but he’s understanding the scheme and how he fits much better, we are told, after an offseason of development and could push his way into receiving major snaps. The team has used Jay Ratliff, last season’s breakout D-lineman and starting nose tackle, at end, hoping to use the two together. We also hear that DE Jason Hatcher has made enough improvement to warrant more snaps. So, who loses out? It could be Marcus Spears, who has made surprisingly few big plays since coming to the team as a first-round draft pick in 2005.