Livan is not a low-scoring teams kind of pitcher. He is reliable in the sense that he usually doesn't give up huge amounts of runs, but he also rarely shuts the opposing team down completely. In the Nats case, 3, 4, 5 runs given up IS huge, and often insurmountable. That is why, by and large, Patterson is a better fit for the Nats than Livan.
That said, Livan is great at soaking up innings, and I believe this game and the sweep are still well within our reach.