Do you need a backup QB if you have the best doctors around? I hired the best doctors, and even though my players get injured, they are still able to fully recover for league games.
With doctors, the players have a lesser chance of being injured, however, if they do get injured, it can still be for a long time. I have max doctors and still get a player injured for 23 days or so on occasion. With doctors, they are ready to go in about a week to week and a half, but will still miss that first league game.