Just added in, in case you've already read:
Man-Cover 3? A traditional cover 3 has both corners and the free safety covering a deep third. In this coverage, the corners cannot allow someone to slip behind them in coverage as the safety couldn't realistically get to the ball in time, so you see corners surrendering the underneath stuff and not breaking on short routes until the ball is in the air. In Seattle, however, Earl Thomas is so damn good, corners are able to break and squat on the underneath routes, giving the defense more man-coverage elements... and weaknesses.