It certainly does seem that these guys can tell ACL/MCL on the field these days, based on the particulars of the injury. We had a LT get hurt (ACL) in HS and the trainer and Dr. on the sideline diag'd it and sent him to get the MRI to confirm. He had surgery after swelling subsided, a couple weeks later if memory serves. They obviously couldn't be 100% sure, but they knew based on how it happened and where the pain was. If they can tell that in smalltown NH, they certainly have the best people on the sidelines at an NFL game to properly diagnose injuries.