Training camp is a time of hope for NFL teams. The grind of the regular season hasn't begun yet. There are no teams out of contention playing out the string. Every squad is 0-0 and optimistic that a successful campaign is just around the corner.
However, there's a dark cloud that can move in and blacken out the summer sunshine. One thing that every team tries to avoid above all else this time of year.
Serious injuries to prominent players.
Nothing takes the wind out of a team's sails and casts a pall over the practice field like watching a starter go down early in camp.