Chris Brown has a column on Grantland today about how dynamic safeties like Reed and Polamalu have changed the way NFL defenses match-up to the latest offensive schemes. He also outlines some of the evolution of defensive schemes from the 4-3, to the 46, to the Tampa 2, and now the Cover 4. There's also an interesting footnote about the Desert Swarm defense implemented in the 1990's by Arizona.
Michigan's defense still has a long way to go, but we finally have a coordinator on the front lines of this evolution. We also probably have our best pair of safeties since......since....hmm......Welbourne-Murray? I don't think Kovacs-Gordon are THAT good and still make their share of mistakes, but the bar isn't set very high for a pair of Michgian safeties.