There are only two reasons why employees don’t do a good job. They either can’t do the job, or they won’t do it. If they can’t do the job satisfactorily then the solution should be quite obvious—they should be transferred to another position or eventually they may have to leave the company. As harsh as this may sound, most people will find a position which will make them more successful and happier.
The other reason for people not performing well is more difficult to solve. There are many individuals who have the right experience and the capability to perform well, but for some reason they don’t. As a supervisor, you need to determine the problem and fix it. Before you jump to conclusions about the cause of the problem you should do one thing. Talk with the individual. In some cases, the problem has nothing to do with work. It could be a personal problem.
Another way to determine the cause of the problem is to listen more attentively. In many cases they are giving you signals with their comments or actions because they are reluctant to tell you their problems. Improve your communication.