Not sure Atkins should be in the team for Wembley. Won't be match fit and unfair on King who has been great. If talking about a bench spot, Sita will be fitter even if not as good a player as Atkins and this will be vital against a big solid and rested team like Catalan.
I reckon Atkins will need to play v. Cas. Must be someone who fancies a rest. It would be lovely to have a rest a week before the big game ... so long as your spot is secure.