Buying or Selling Job Security for NFL's Most Tenuous Starters

Training camps are in full swing across the NFL, which means that it's time for lower-level starters to be challenged by new offseason additions and young up-and-comers.  Every NFL team has its own weak link, where a starting job is teetering on the edge of going one way or another.  In other situations, teams might have a weak top option at a position but failed to address the need properly in the offseason, leaving the current starter unchallenged. Which current NFL starters are the weakest ...