From a medical stand point the types of injuries really come into play here. The muscle strains can be blamed on the training staff and strength and conditioning staff, the packers have an alarmingly high number of groin, hamstring and quadriceps strains. This is a direct result of a lack of an effective warm-up and strength and conditioning program.
As far as ligament sprains go, this can be a little of both. It's a collision sport with high risk. When two people tackle each other at a high velocity there is a risk the player coming in with less force will sustain a ligementous injury. However, there are strengthening programs these players should be on. The medical staff should be performing individual player evaluations to determine abnormal gait and foot patterns, then develop a specific program for that athlete to work to fix it. For example if someone is an overpronator (the foot turns inward during mid step of gait-very common), you are at risk to sustaining lateral ankle sprains, high ankle sprains and ACL/MCL sprains. To fix that, we would strengthen your peroneal muscles and work on agility training after.
As far as fractures go, it's due to the sport. Anytime you fall on an outstretched arm you are at a high risk of sustaining a fractured collar bone, wrist or arm. When 230 pound Danny Trevethan at 80% speed (estimation) hits 225 pound Aaron Rodgers at 25% speed (estimation) Rodgers is placing upwards of 2,000 pounds of force onto his arm.