Your players are obbviously getting injured because they are not physically fit nor strong enough to play at the level they are at. Unless you know what you are doing, training your players can be dangerous to their mental and physical ability. That is why you have to keep using booster drugs to keep their levels up. They have become dependent on you feeding their habit and you are running out of money and patience ( this can be a virtue sometimes).

They only way to get them to be strong again is to go cold turkey ( not the country) and to train them at max intensity, till they are red in the face and often. Before you cross those bridges, you can burn them, as well