I think that part of the confusion is the terminology. These used to be called separated shoulders....and there are varying degrees. Sometimes a first degree (and maybe even second degree) was called a sprain....because there was nothing torn. However, because people confused separated with dislocated, they seem to have started using the term "sprained" for all AC joint injuries. A grade three, like yours (and which I also had) means that a couple of ligaments are completely torn. A week out of such an injury, I doubt he would be able to lift his arm above his shoulder....making throwing the ball difficult. I do remember that someone, I think it was Brian Griese for the Broncos, finished a game with a grade 3 and was sling the ball side armed because he couldn't lift his arm....but probably not something you want your quarterback to try.