A counter-tactic chess move is necessary for the hack and slash 100% injury rate setting.

My recommendation:

Red tab on each player's card with the ability to click it and 'restore the player to full health.'

1-time usage - 1-time on a player - 1-time on whole for a season.

If you want to protect the sanctity of the playoffs have the restore to full health ability expire at the trading deadline and disappear along with the red 'trade' tab.