Schmeichel had a very good season last season, and was seen as one of the best in the league, has seemed to of gone off the boil
Adrian got called up to the spain squad, cannot get past Darren Randolph now
Heaton & Pickford average shots on goal are significantly higher than other teams so the stats can be scued there (e.g 1 good save when not doing anything for 70 minutes is a talent not all goalies posess)
This time last season Fraser Forster was keeping clean sheets left right and centre, and is having a bit of a wobble at the moment.
Basicly it is ver very hard to judge who is better and who is worse! Joel could have a fantastic 12 months but could regress during that time. But right at this particular moment i think he is just as good if not better than most of the keepers mentioned in this thread as possible replacements