Too many people put too much reliance on not only the very last game, but the very last inning. The guy is a major prospect for a reason, he didn't just bubble up from the ground with no minor league success.
That said, his first 10 innings in the major leagues were scoreless. That shows alot of potential, even by the common "what did you do for me yesterday" attitude. He broke down in the final 1.1 innings, unfortunately, but the endurance and composure will come with time.
He might not set the world on fire this year, but he's not exactly out of control, either. I think we can rely on him as, at the very least, a great 4th or 5th starter on your fantasy team, and he will probably show more flashes of brilliance than your average bottom half starter, too.