A new DC would be Gruden's 4th - right? Btw - I don't think Gruden *chose* Haslett. In fact, I am willing to authoritatively state that Snyder himself nixed the idea of paying Jim Haslett not to be the defensive coordinator, particularly since Snyder was already doing so with Mike Shanahan who was let go before his contract was up. I think the team justified the move as being helpful to Gruden, a first time head coach, with the idea that his first year would be steadied with Haslett on board and having significant previous head coaching experience.
Gruden gets a pass from me for Haslett.
Of course - then he hired drinking buddy Joe Barry for the job. What in God's name lead him to believe that Barry was suddenly going to become a dominating DC after zero evidence he could do the job at other gigs - I do not know.
By comparison, Manusky has been Bill Parcells. I'm not a fan of firing coaches because of fan outcry that there 'has to be major change'. If Manusky truly is deemed incapable of consistently fielding a top 10 defense, then fine - let him go. But I really hope they aren't going to do so to satisfy fans. Our D has shown some relative progress under Manusky and if you don't think we can do worse, I'd suggest that's a risky belief.