You either hired them that way or you made them that way.
W. Edwards Deming, one of the truly great leadership gurus, gave us those thoughts about "low performers."
There are some people who are just not productive. They are not productive because of ____________ (fill in the blank). There are many reasons why one person is not getting results. Deming says there are one of two reasons why you have low performers.
They were low performers when you hired them. Bad hiring - bad mistake on your part.
They were satisfactory or even good performers when you hired them, but through poor management, supervision and leadership, they have become low performers. Bad supervision - bad mistake on your part.