An emphasis on evaluating and developing linebackers has come under the spotlight in recent years. One reason is the ability of linebackers to match up in sub personnel situations. With offensive sets using more multiple spread formations, the pressure on the defense has increased dramatically.
By design, defensive coaches are implementing more athleticism and versatility within their linebacker corps and their defensive schemes. This is why you're seeing college safeties projecting to outside linebacker when coming into the NFL. This allows defensive coordinators to put more athleticism in space on defense, which improves their matchup ability in sub personnel groupings. Two great examples are Cato June of the Colts and Carolina's Thomas Davis.
The majority of teams are looking for linebackers who can play and be productive on all three downs in regular and sub situations. In addition, scouts must project whether players can come in and contribute on special teams units as rookies.