The Falcons had guys on the sidelines for the same reason.
Listen to McCarthy's spot-on assessment after last week's game. The CBA puts a serious dent into teams because these guys don't get to practice as much. I personally also believe that the style of play is pushing towards more injuries, meaning that players are more specialized. They go on and off the field for game situations, resting their muscles and then pushing them to 100% for a play or two, then back to standing or sitting on the sideline, then back to 100%... Players used to play more of a complete game, and probably not at 100% every play but at 80-90% to save some for the rest of the game. Their muscles weren't maxed out in the same way.
Don't forget that even with nutritionists, strength coaches, team-provided foods (in camp), and everything else these 20 year olds still make bad food decisions. Eddie Lacy is the obvious example of someone that can't put down the fried catfish, but lots of them eat garbage when on their own. That leads to hamstring pulls and such when your muscles don't have the right vitamins and nutrients to play at such high levels.
My opinions.