Last season before the finale, it was reported that he couldn't go more than a short period of time without something coming out one end or the other. This would likely be an issue if you wanted a guy to play goal at a high level for 60 minutes.
This year, we have literally no idea what the injury is/was, or how long he has had it.
You can speculate all you want, but there is zero evidence for your statements about his mental toughness. It's a theory, not fact.
I think that for $7m+ and given how he has performed in the past, fans have every right to say that Rask needs to be better when he's in there. However, seeing as we have no idea what's wrong with him, I don't think fans should be questioning it if he says he can't go.
Last time I checked, the Preds are better than the Isles for the season (89 vs 82 pts) and have played better of late (7-2-1 vs 4-5-1), so if Rask was going to "tap out" of a pressure situation, wouldn't he have been better off bagging on the NAS game instead of NYI?