I think Marcus has had his fair share of plaudits over the past few seasons. The worrying thing for me is that Marcus hasn't made just one mistake. He has looked iffy with a number of different areas of his game this season and doesn't look to of made too much of an improvement in sorting them.
I think that the lack of another quality goalkeeper at the club has made him relax (that's human nature) and maybe he needs a little shaking up and to have some pressure put on him.
The thing that really bugs me about the mistakes he has been making is that I know he can do better - Maybe what you are seeing on this thread is more frustration than anything else.
Unfortunately Marcus isn't the number one at a lower league club without expectations any more - he is an International keeper at a Premiership club. The nature of the beast is that if you don't shape up then you get moved on.