This year in particular BB has rolled the dice on plenty of players with torn ACLs. Easley with two rebuilt knees is the headliner, but Gronk is recovering also. Tom Brady and Logan Mankins are both ACL retreads. NESN reports that defensive end Will Smith, DT Tommy Kelly and LB Darius Fleming all popped their cords in 2013. Wes Welker started the trend with an incredible comeback. For icing on the cake, BB might sign Dustin Keller, another 2013 ACL victim, after June 1. Then there's Vince Wilfork recovering from his Achilles. A number of pundits have bet their (two bit) reputations against Wilfork's recovery. We'll see.
I compare this to the Jets rolling the dice on shoulder injuries. They drafted two high first rounders a year ago, both with shoulder injuries. Dee Shoulder Milliner had an injury-filled rookie season with calf and hamstring injuries. He looked good when he was on the field. Sheldon's Shoulder reinjured his you-guessed-it in September, but he looked good after he recovered.
My suspicion is that shoulder injuries can be hidden but they slowly affect production more and more as the tearing piles up inside. Players learn to shy away from shoulder contact. On the other hand, modern ACL injuries are fixed and then the player's knee is as good as new.
Denver rolls the dice on old age. Peyton has undergone plenty of surgeries in his time, and Wes Welker has taken vast numbers of horrible hits. Welker's brain will become a prized piece of medical research real estate someday after his spirit vacates the body.