He must've slipped a lot because you don't trade good players for picks when you're a contender.
See, that was my first instinct when I heard it. But the fact of the matter is that that rule is much more applicable to basketball where superstars dominate the league. But in football, it's really different. Instead of 12 or 15 players, there's 53 on the active roster, so each player has an inherent lesser value.
Furthermore, whereas Kevin Garnett can play nearly the whole game in the playoffs and impact the game offensively and defensively, Seymour only played the defense. So by the nature of the game, he can only impact less than 50% of the plays in the game (because of offense and special teams), and that's not even counting the fact that BB would've subbed him in and out anyway.
Overall point is though while I'm a little reserved about seeing him go, I trust BB and think he has the best interest of the team in mind.