I'm guessing there was some concern that he might not return to previous levels next year. Fastball velo is down over 2 mph and he's not inducing swinging strikes. Hard to complain about them deciding to cash out now for a guy they find intriguing rather than roll the dice on him increasing his value a bit next year. He only has one season as a high-end reliever, so it's far from a given that he returns to that level.