Ah, the 91-Day Wonder. They provide just enough performance to get past most 90-day evaluation periods.
If it's happened to you, don't feel bad. This could happen to almost any hiring manager for any position, although sales managers may feel this more than anyone based on the example I'm about to provide. For some reason, they seem to be the most likely targets for this little scheme, which you'll understand better as this story develops.
Hiring new employees can be a risky business, though it doesn't have to be. One of the more common mistakes I see in the hiring process is screening in candidates to the pool of finalists.
What exactly is screening in? It's the hope that you'll end up with a nice selection of final candidates to find that diamond in the rough. Making exceptions, creating shortcuts, or whatever means you use, but the result of the problem is that you intend to compare candidates to one another.