The misconception I think arlen has is that players just don't come back. If you budget for medical, they always bounce back to 100% from minor injuries. And, again with high enough medical, they will bounce back from major injuries if you allow them TWO recovery cycles. I assume arlen takes his players off DL as soon as they're available. If you think about it as "recovery from injury" for first recovery cycle and "rehabilition and return to form" for the second recovery cycle, you'd leave them on the DL. If you twist your ankle, you can run again 7-10 days later. With a slight limp. Wait a month and you're back to normal.
The one exception is a late season injury. If you get a major injury at game 120, you're a bit screwed. You'll only get one recovery cycle. And it won't be a full recovery.