His numbers have been strikingly different. He used to give up too many hits/HR's, but recently, he's done the opposite - issued a lot of walks while keeping the ball in the park and allowing few hits.
He didn't really give up a lot of HR's in his first stint. Just 3 in 53 IP which is amazing (hasn't allowed a HR since being recalled also). His problem was that he allowed a lot of hits because the Nats defense let him down. He had a .367 BABIP in his first stint. What is unusual though is that he had a decent K/BB rate in his first stint, but now he is walking more guys than strikeouts. He obviously isn't as good as his ERA in September, but I think he can be a 4 ERA guy next season. The key for him will always be if he can control his walks.