The manual has been updated and it addresses several new issues. At one point under WORN OUT it states:

"Worn Out players are automatically farmed before a series starts by the system so you will not be able to use such a player past the series in which he became worn out. This condition is only for the season in which he has been "used up" If a player becomes worn out during the regular season he will be again available at the start of the play-offs if he does not have an overlapping injury."

I think this is pretty clear and if we don't know it, it is our own fault.