At this point, Adalius is the only one who's past performance makes him a lock as a three down LB.
-- Woods, despite several detractors, showed promise, though apparently not enough to get him tendered at more than a second round compensation or offered a long term contract (though they could be counting on an uncapped 2010 extending him another season as an RFA).
-- TBC provided a decent pass rush before he left, and while he was better than his detractors would allow at setting the edge, he wasn't the best at it either.
I can see Pierre as a two-down OLB, replaced by TBC on passing downs. Not the ideal, but you get enough of a pass rush from Pierre if they pass on 1st or 2nd down, and TBC provides enough against a run play on a passing down. I can't give either the edge in coverage yet, but they might address that by switching up the coverage assignments using Mayo, Guyton, and Adalius differently.
Redd got more reps last season than I had expected. He must have pleased the coaches to acquire at least three Practice Player of the week black jersies in addition to the rookie reps. He has the size to set the edge - he's also got experience at Virginia and Liberty as a 3-4 OLB and 3-4 DE. Their postseason film review would have included practice and game film and he might have graded out much better then expected.
Craig was a high school LB who was switched between LB and DE at Cincinnati. I'd seen him play up on his feet and not look out of place both in college and his All-Star game. It may be he's ahead of the curve.
Crable is the big unknown.