Robin Ross coached 46 years with stops at 12 Division I programs, 2 years in the NFL, and 9 years in the CFL. His experience has taught him that linebackers can't be successful if their eyes are not in the proper place.
You will see a video excerpt from Coach Ross' Glazier Drive clinic LB Run & Pass Technique and Drills.
Linebackers versus the Run and Pass
Eyes: The proper use of their eyes is important to a linebacker as any other physical skill. What a player keys and sees will help him react. He must see correctly in order to make the proper reaction. This is Stimulus Response.
Feet: Feet are important for every football player. They can't be successful if their footwork is not efficient.
Hands: They need to know how to deliver the "hand shiver" and where to "Strike" and grab the offensive player.