re: Mett has a torn ACL per ESPN (links)

Well since the Mechanism Of Injury was a severe hyper extension of the knee this was the most likely ligament involved. I would just hope that the brace protected it enough to limit the tear, though seeing how much pain he was in it might not have helped much. And yes they can perform a Lachman's or Anterior Drawer test to determine ligament stability on the field or sidelines but it would still need an MRI as previously stated to determine severity and other possible ligament damage.