I'm pretty sure Wigan have rested players before big games over the years. Sean oloughlin one year only played two games in about 2 month and that was challenge cup final and grand final. Shaun Edwards never played the week before Wembley.
Cas have rested players for the biggest game in there super league history so far and certainly not to get at Wigan. Not all things rugby revolve around Wigan you know ?