That's the way I see it too. I've said it in the last week or so, as it stands, I can see Santon coming off the bench for one of Simpson/Raylor if either one of them are having a particular rough time on the pitch.
Can't see Pardew doing that, myself. Think he'd be worried about the loss in confidence of the substituted player. (Unless it's Cacapa esque).
Well he did it with Simpson against Spurs so he could do it again.
Mainly because of the threat of Bale against tired legs or something? Simpson had done okay iirc.
Bringing Santon on was more of a message to Simpson I thought. Danny was a bit meh that day imo.