Natcho was here essentially because he wanted to rid himself of Rubin Kazan. He wanted to become available for a move to a better league, for free, preferably with CL play already guaranteed. While he did end up back in Russia, it cost CSKA nothing to get him, and he got what he really wanted.
That said, I'd take him back in a heartbeat. One of the few times I've seen a "slow" player have so immediate an impact in Greece. Let's not forget his inclusion immediately pushed Tziolis off onto the bench (and then off to Turkey). Win-win, really.