Ranger, your question isnt as easy as you think. You're going down the wrong path. Many factors effect if a WR can catch a thrown ball. Just to name a few; DB coverage, pass depth, wr attributes, pressure on your QB, etc...
If you want to understand how good your WAs, and thus if you should throw to him, look at his WR attributes relative to other DIII WRs. For example, if you perform this analysis on your RBs, TEs and WRs you will see which is your best option when throwing a pass.
After that, try working on pass depths amongst your pass options versus the opposing teams defense and see if adjusting these allows your WR, TE or RB to become "more open".