If I remember correctly some NFL great LBer's were "tiny".
Mike Singletary
Sam Mills <R.I.P Sam>
Jessy Tuggle
Just to name a few of the "tiny ones", they werent that blazing fast either. Dat is the "Rudy" of the Dallas Cowboys, first to practice, last to leave, he has heart and determination. Most small people have something to prove, I know because Iam one <5'8">, Dat plays with a chip on his shoulder as he should, Coakley was the same way. This is why Doug Flutie was one of my all time favs, every time he plays he puts his heart on the line, like I did at Southwest Texas state (which is now called Texas State, Go Cats!!!). I was a tiny outside LBer, but I laid it on the line everytime I played.
Us "shorties" get sick of people saying we cant do this, or we cant do that, its easy to get "short man syndrome" that way. This is why I have a ton of respect for Sprolles and Dunn, and Spud Webb was my favorite NBAer.