I'm going to say Roy W is better in coverage... KD is just a special teams demon. Roy did cover well in his rookie year... when he's playing shallow zone that's okay... prob is, the nickel LBs play shallow zone... So when the linebackers are playing zone, either Roy is blitzing, or playing deeper than the LBs... which usually spells trouble... Roy usually can't cover top flight WRs... Now... Roy will shine even more if we get a consistent pass rush next year... sign a proven OLB/DE, like Abraham things might change... Paying a guy like Abraham handsomely wouldn't hurt my feelings.
Now on the other hand... I'm going to compare Roy to Troy P from Pitt... Pitt has a madhouse pass rush, they've had the same defense since Cowher came aboard... that's 1992 and thirteen seasons of blitzing.... Pitt can afford to do whatever they like with Troy P because you have Joey Porter rushing the passer... Pitt can absolutely get after the QB, and with their blitzing, you never know where it's coming from... Dallas really isn't that deceptive with their own 3-4... So we'll give it a little time... say next year... hopefully.
Now does that equate to Dick LeBeau is a better DC than Zimmer? More experienced in the 3-4?? Absolutely... When you get either safety in a chase mode and you can contain the blitz... It doesn't matter about being able to cover when you're chasing a TE or nickel WR all the time... It's about disrupting the opposing offense's scheme to take advantage of the talent at hand...
Solution... rush the passer effectively and you get good looking zone coverage that usually works... rush the passer inconsistently and then you get into a chase mode because the QB is completing short intermediate passes with a spread out offense that forces your safeties into coverage.
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or Kevin Smith