Well the short answer to both of these questions is no and yes, respectively. I personally feel that he's going to be a very good closer down the line. The stuff is certainly there and he's shown the ability to clean up a big mess and get big outs. He's also shown that he can pitch well in the playoffs, which in New York, as we all know, is very important. Yet he's struggled his first two times out there and has converted one of the two save opportunities he has faced.
People can say what they want about the ninth inning being the same as any other inning or that you can put just any guy back there and he will get the job done, but that is certainly not true. It definitely takes an adjustment going from the eighth to the ninth as D-Rob has shown. I don't really believe in the whole 'closer mentality' thing, but there is an added pressure to pitching in the ninth, maybe there shouldn't be, but there is and there's no denying that.
Robertson will have tonight off (I would hope) after two very stressful outings in which he threw a lot of pitches and hopefully this will help him clear his mind. Boone Logan said after the game that maybe he was trying to be too perfect and not being who he is. This is very possible, and we just have to hope that he gets better with more experience. If this doesn't make you feel better, maybe this Jack Curry tweet will.