Realistic Injuries
 

The game has made progress on the injury front by adding setbacks. But to make injuries more realistic, injuries shouldn't be so deterministic. Almost all injuries should be day-to-day. It will then be left up to the manager to determine a player's performance is being too adversely affected by an injury to continue and they should go on the DL (or not).

Based on medical reports of some kind, the manager can decide when a player is ready to come off the DL. They may need to send the player to rehab assignment to see if he can play ok. You can choose to rush him back at the risk of poor performance or further injury. You may make different decisions based on whether you're in the playoff hunt or not.

Use the the team doctor like scouts are used now... they give their advice and their reports. But they don't know with certainty how long the player will be injured.