This might not be an event that you are particularly familiar with, but it seems to be an idea with great potential value. Over the course of the past two days, the NFL held what it called the Regional Combine Invitational, and it provides a critical opportunity for players who otherwise would not be in the public eye to get in contact with the teams around the league, where a relationship can develop from that.
The Regional Combine Invitational began last season and consisted of veteran players with three years of experience or fewer. They were invited to essentially participate in the equivalent of the Combine, performing workouts in addition to undergoing a variety of assessments, such as medical checks.