Sports injuries are like aircraft accidents; if the athletes could see them coming, no-one would ever get hurt.
The short answer to your question is: our inconsistent offensive line has forced our QBs to scramble too much and take too many big hits, and our QBs are holding the ball for too long to try and make plays. And we had a bit of a revolving door at O-line and receiver in the first half of the season, a sure way to get your QBs killed.
Quarterbacks are prone to shoulder problems because:
(1) A QB's shoulder pad on his throwing side has to be compromised a bit, to provide the added mobility he needs to wind up and throw at full power. Look at the small pads most QBs use, compared to those huge pads that running backs and linebackers use.
(2) They're looking down the field so are less able to brace themselves to protect against big hits, the way a receiver or running back can. For example, Buck took a nasty hit that he couldn't see coming on that play when he was intercepted against the Bombers on Oct. 18th.
(3) Their shoulders get worn down throughout the season due to overuse injuries, from weight training and from throwing a couple hundred throws each day in practice and another 100 or so during the warmup and the game.
(4) Some defensive players in this league (Maurice Lloyd, Adriano Belli, half the DBs) are famous for taking cheap shots at QBs. Remember earlier in the season, when that defender coldcocked Pierce as he was hooksliding?
(5) They often take big hits while falling backward, where they have no way of protecting themselves. It is good to see the league is trying to protect the QBs a bit more, but, lets face it, its a rough game where people get hurt a lot. That's the price QBs pay for all that fame and the bigger pay cheques.
Pierce hasn't gotten much respect from the referees. He has been roughed by defenders more times whthout drawing penalties than any starter in the league. Are you listening, Tom Higgins?
Calvillo seldom gets hurt because he has the best O-Line in the league in front of him. And he's a rhythm thrower: almost every throw is on time and usually away in less than 2 seconds. So he seldom takes big hits or gets sacked. That's a big part of why the Als have been so consistent for so long.
Ricky Ray is just one of those guys who never seems to get hurt. Who knows why? Damon Allen was the same way. With huge blockers like Kabongo in front of him, you can see why he doesn't get hurt much.
Burris has a great O-Line as well,. He's very good at sensing pressure and uses the defender's schemes against them to scramble for first downs. He runs out on the sideliners a lot and therefore avoids big hits.
Buck gets hurt a lot because of his go-for-it, fearless style. He takes a lot of extra punishment by holding onto the ball for too long in the pocket, Maybe better pocket movement would helpl imit those hits. Jarius took a wicked hit to his shoulder. That is the first time I remember him getting hurt. I think Lulay hurt his shoulder while getting tackled on a running play. Just bad luck there, I guess.
Finally, there's one quality that's common in Calvillo, Burris and Ray: they are multiple-year veterans who have figured out how to be very effective and consistent, while limiting their exposure to injury.