Finding a "diamond in the rough" when it comes to scouting football players is a rare talent. If an undrafted free agent makes a team, it's considered a surprise. When an undrafted free agent ends up being an awesome player, it's comparable to finding a diamond while mining for coal. The New Orleans Saints found it in running back Pierre Thomas 5 years ago.

Some of the great undrafted FAs signed with their teams shortly after the draft ends. Others went on to play Canadian or Arena football before breaking into the NFL.

Hall of famer Warren Moon played quarterback in Canada before mastering the "run and gun" offense of the Houston Oilers. Future hall of famer Kurt Warner was slinging it in NFL Europe and the Arena league before winning league MVP and Super Bowl MVP with the St. Louis Rams.

The ranked the top 10 undrafted NFL free agents of all-time. Click here to see their rankings.