A good physical comparison for Ratelle would be Chris Borland, the former tackling-machine from Wisconsin, who famously retired after 1 year in the NFL due to health/concussion concerns. Borland was an under-sized ILB drafted in the 3rd round by the 49ers & played his way into a starting role his rookie year & had over 100 combined tackles in 1 NFL season. Borland was power 5/Big 10 stud vs Ratelle excelling in FCS, but Ratelle's pro day numbers are all much better than Borland's combine numbers. Not saying Ratelle should or will be a 3rd round pick (I believe he will go undrafted) but he definitely deserves a shot...
http://www.nfl.com/combine/profiles/chris%20-borland?id=2543772