Very tricky thing to do is first weed out guys that are defensive ends in college that will be 3-4 OLB’s in college. We first try to identify a position, but often list both possibilities. If it is close, for example if a defensive end is a bit undersized, but moves really well in space, they very well might be an OLB in the NFL.
Most of the scouting reports we do on DE’s are for ends that have noticeable pass rush ability. There are some that are much more adept at stopping the run than getting into the offensive backfield, but that is not as much a premium type prospect trait.
The frame of the player is important. Looking for height and arm length. Many players are slowly growing into their build. Player could be 6-5 and only 250, but was 6-1 and 185 as a freshman. In the NFL, that player could grow even more.
How many sacks and TFL’s?
Can he “convert speed to power”. It is like ability to quickly build momentum to knock blockers back.
Long arms help with ability to defend against the run.
Have an array of pass rush moves? Some players just bull rush, but it is very important to have some other moves that they are developing such as the speed rush, rip, swim, etc.
Have some knocked down passes?
Does his motor run hot and cold? – This indicator most of the time carries over to the NFL, rarely fixed.
Able to chase down ball carriers?
Able to drop back into coverage.
For bigger guys, it is very valuable if they can move inside to tackle on 3rd down and obvious passing downs.