And they also spent last season's free agency and draft to improve Ryan's defense. Now they've totally given up on him after one injury-riddled season and blamed the early season losses for the change. Nevermind that he duct taped the shit out of the defense with off-the-street players. Jerry Jones likes to change just for the sake of change, and keep his team in the news during the playoffs...even if they're not still playing.
Already touched on but good corners aren't something that's specific to a scheme. The type of play they do might be different (press versus coverage), but it's all about trying to prevent passes. In this passing NFL, a scheme like the Tampa-2 might be preferred. The Cowboys have the personnel. Here, I'll run down the list:
Ratliff - From NT to DT, but won't move out of his 1-technique spot.
Hatcher - From DE to DT, but won't move from his 3-technique spot.
Ware - From WSOLB to WSDE, will be coming from the same spot but from having his hand on the ground, which actually would be preferable. Ryan put him too much into coverage.
Spencer - From SSOLB to SSDE, something he already did in the Nickle so it's not a huge adjustment.
Lee - From MLB to MLB, anyone who's been paying attention to this team knows Lee is going to thrive in this scheme.
Carter - From MLB to WSLB, someone else who'll thrive in this scheme.
Albright - From LB to SSLB, one question mark but given he'll be on the strong side he won't be asked to do too much.
Carr - CB to CB, already touched on corners.
Claiborne - CB to CB, and again.
Church - SS to RS, his return will increase play in the secondary and he's more than capable of getting the job done.
Sensabaugh - FS to LS, not a big change.
The shift won't be as big as people think. If anything, the personnel are maybe one LB short of being perfect. Spencer is a big ? and I don't think he'll be back next year because of the cap issues, but finding DEs for a 4-front defense isn't nearly as hard as finding someone to shift to a 3-4 OLB. Should probably note that since the switch to the 3-4, Dallas hasn't really been lighting it up. With the exception of the 2009 team, which was 2nd in the league in points against, they've all been pretty mediocre. Maybe a switch back to 4-3 type will be good. Oh, and Ryan wasn't who Garrett wanted. He wanted Horton out of Arizona. Ryan was a Jerry "splash" hire.