I have a general rule in fantasy football: One week is a fluke, two weeks is a trend and three weeks is a pattern.
Generally, what that means is that I'll pay attention to anything that happens in a week, but I rarely react to it with too much excitement or dread. If a random player steps into the starting lineup and blows up, I'm not going to make him a must-start player based on one game. Likewise, if a star struggles, I'm not going to automatically bench him. My radar has been dinged, but we're in the monitoring phase.