Everyone will talk about that brainfart. Thing is MAtS is such a keeper that when he's developing, he'll make even more silly, idiotic errors. I don't see any other keeper required to follow this path of learning, except Valdes and of course Neuer (in Schalke). He's not going to be a pure shot-stopper like Courtois, he's going to play like Neuer: being a sweeper keeper. What's important, is that he doesn't get down because of this and the team keep supporting him. That's what happened this match. He apologized and everything was calm once again. And he paid it back well (although the penalty itself was pathetic). He'll learn.
He's WAY better than he was two years back or so, he was making even bigger mistakes than this.