I would say level 5 doctor is too much downgrade to level 4 because they all do the same thing. Instead of investing into doctor I would invest into game shape trainers. I am about to hire another one I get to division III. Its all up to you my opinion and I really did some intensive work back in the beginnings day of buzzer beater.. Is that doctors are not needed for 1-2 weeks of salary wasted just turn your player into a club development player. Doctors are only needed for national team level quality players.