I'm assuming this wasn't the kind of injury occurence that you were talking about in your initial post? (not sure if you actually saw the Bell hit, but it was very reminiscient of the Gronk hit -- just a guy coming across the middle and getting a direct shot on his knee). This wasn't a guy getting injured because he was wearing down under a heavy workload, or getting beaten up during a 30 carry game....this was just the unfortunate "wrong time, wrong place" kind of hit that happens from time to time in the league.
Bell's *extremely* fortunate that this wasn't a MAJOR injury requiring months of rehabilitation. So while we're obviously not happy that he's dinged, the bigger picture is that our star RB didn't get his knee completely shredded (and frankly, that's what it looked like on the initial replays
One of our LBs, Sean Spence, had a very similar-looking direct shot on his knee two years ago in his rookie preseason, and he's only now playing (his 3rd year).
Again though this wasn't some kind of overuse /weardown injury. The only way you could prevent Bell (or Gronk for that matter) getting injured on a play like this is to never send him out on a pass pattern.