No I don't blame him for the pen miss but in that situation - given how good he had been as you rightly point out - it's disappointing for him not to have put it away.
If we had conceded straight away from that pen miss I may think differently, mind, but ultimately Martinez facilitated our downfall with that change, and he was then let down by the defenders as well.
As I've said, i've not turned on him completely but now I am starting to very much doubt - like a lot of people who want him out do - his ability to change.
To me, in the last few games since the turn of the year we have shown signs of improvement and in some games being excellent. However, there comes a point where signs aren't enough. I thought everything we and he did yesterday was fantastic (bar the pen miss) up until the 76th minute.
I said at the time it was a baffling substitution and as soon as they scored I had very little doubt they would go on to get more goals. And that's why it's so horrible to take - because he had done all the hard work and then messes it up with something that was quite frankly amateur - and the experienced and 'best squad we have in years' lacked the mental capacity and toughness to see the game out.