So I'm reading Fields has an AC joint injury, not a dislocated shoulder. I've suffered AC joint injuries 3 times in my life. He basically tore a ligament(s) that keeps his collar bone in place where it attaches to the top of his shoulder blade. Really it all depends on if it's a partial tear or it's completely torn. If it's completely torn his collar bone is floating and is simply being held in place by his skin - if this is the case, he should sit for 2 to 4 weeks.
If it's a partial tear, he can play. He just won't be able to lift his left arm above his head, and he'll be considerably weak in that arm too. I always got a nasty bruise that starts on the pectoral and sometimes goes up the neck....and a lot of swelling. It sucks, but he could play.
In all honesty, the pain isn't that bad. It's mostly swelling and weakness. I doesn't hurt that much. That joint is all about lifting your arms over your head, it's not like a dislocation or rotator cuff injury.
Your friend, Doctor Black Rainbow.