SOLUTION
The solution to the performance problem is to develop some kind of feedback mechanism so the poor performer gets regular information on how well she is performing. Production reports, counseling sessions, timely performance reviews, regular performance feedback discussions, etc., can all serve to provide the necessary information to keep performance at acceptable levels.
Aptitude Problem?
For very complex, challenging jobs, a performer who is motivated to perform and who is given training, practice and feedback still may not be able to perform. Such might indicate an aptitude problem. If you think this might be the case, click the link below:
Analyzing and Solving People Problems
Solution Explanation
The simple solution to such a problem is to develop some kind of feedback mechanism so performers get regular information on how well they are performing. Production reports, counseling sessions, timely performance reviews, regular performance feedback discussions, etc., can all serve to provide the necessary information to keep performance at acceptable levels.
You should seek ways to keep the performer informed of his performance level so he can "self correct" his own performance as necessary.