What I am wondering is whether what you are calling a scab is necrotic tissue instead.  They don't look a lot different.  Necrotic tissue is dead, typically black and leathery looking, attached to the live tissue underneath, very smelly if there is moisture around the edges.  
a scab is usually more irregular, does not smell, is a collection of exudate that has dried, whereas necrotic tissue is skin and whatnot that has died in that spot.  It needs to come off before the wound can heal -- but if tendons are exposed below it you do have a problem.  In people it is surgically removed then irrigated well and dressed with something like Silvadene or neosporin.  If it is necrotic tissue you may have to remove it a piece at a time.  Hard to tell the difference not being there, even a good pic may not do it, but let's hope you figure out a way to do a pic.  You may have to cut rather than pull it off.