With everyone in the league going to the 3-4 and the Tampa 2 going out of style, the 4-3 players are getting greatly undervalued around the league (while the 3-4 players are getting greatly overvalued). If I'm a new head coach taking a gig I'm immediately taking advantage of this by bringing in a great 4-3 defensive coordinator and taking advantage of all these firesales of Glenn Dorseys and Derrick Johnsons around the NFL while everyone is looking for 2 gappers and big linebackers. That's how Polian and the Colts have been restocking their D with the league's scraps the past 5 years.
And if John Fox, Jeff Fisher and Jack Del Rio are fired in the offseason, I would be awfully tempted to hire one of them as a DC (although I assume Fisher will have his choice of HC jobs) and move to a 4-3 if we hire an offensive minded head coach. I assume Spears is going to get paid elsewhere by one of these 3-4 teams and that's one more player 3-4 player we'll have to replace. Spears may not be a difference maker, but those 2 gapper strong side 3-4 DEs are not easy to find in the current NFL climate. That's how Tye Jackson gets drafted with the 3rd pick. If the name of the game is putting your best players in position to succeed, I personally think a penetrating 4-3 system suits Ware and Ratliff extremely well.