There are a couple very simple keys for any fan to see if the Cyclones are playing up to snuff on defense. The first one is obviously defensive rebounds. If Iowa State's opponents are cleaning up many of their own misses, that is a gloomy sign. Defensive rebounding is all about effort and discipline.
A fair analogy would be a running back picking up a loose pass rusher in football. The quarterback might get drilled if the running back doesn't pick up the blitzer or the quarterback might get off a quick pass before the blitzer gets there and you dodge a bullet.