Injured players recover a little every night on their own. A doctor speeds this up: each night there is a chance that the player recovers an extra day. The better your doctor, the higher this chance, so a top doctor can almost halve the time a player is out.
To hire a doctor, build the Clinic (Medical Department, level 2). The Hospital (level 5) makes your doctor work more efficiently. Your doctor also gains experience while treating injured players.
Your staff