Originally Posted by Rey
That's why you routinely see DE's placed at 34 olb.
34 mlb need to far more agility than the OLB's.
The DE's that are placed at 3-4 OLB are guys that can really athletic and can rush the passer, but are not big or strong enough to play with their hand down. Some guys, like Sam Montgomery, do not have the agility or athleticism to do so. That's why 3-4 teams stay away from them. Other guys, like Aldon Smith or Demarcus Ware, have that agility and can play on the edge and rush the passer while still being able to drop into coverage.
OLB's have to play on the edge, rush the passer, and set leverage. This means playing in space. 3-4 ILB's go downhill and fill gaps. Instincts and tackling ability are much more important than agility for an ILB.