He is average. He's the Brandon Carr of the LB's. What was Lee supposed to say? "Yeah it's not a big loss at all. He's just average". It's called coach/player speak. He's not a great talent but will be missed because of our depth on defense and any player competent that goes out the lineup is noticeable on that side of the ball.
He could say "It's an unfortunate loss, but we all know injuries are part of the game. Someone else is going to have to step in and step up." Or something like that. You know. The standard platitudes.
I'm sorry, but to me, when someone of Sean Lee's caliber refers to a player who will be out due to injury as a "big loss", it means he's more than just "average".