In any sport, a team of qualified medics can help players recover from injuries and get back onto the field. Blood Bowl is no different and Apothecaries (as they are known) can be very, very useful. However, some teams can't get such medical professionals no matter how much they pay as it is just too nasty a job: Undead, Necromatic, Khemri and Nurgle teams.. I guess you just cant pay enough to sew up battered, pre-killed corpses (even to medical students!)
However, in some circumstances these other teams can attract the assistance of Igor, the famous henchman of mad scientists:
Igor is a master of needle and thread on rotting flesh, connecting hip bone to leg bone, rewrapping funeral wraps and so on. He can really get the boys shambling back to the pitch
Having an Igor on your team means that once per game (only) you can reroll a failed regeneration attempt of an undead player.