SOLUTION
Rather than arranging formal training a skill practice or skill maintenance program is indicated. In other words, provide an opportunity for the poor performer to redevelop his dormant skills through "refresher" training or practice sessions.
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
Police departments learned long ago that if they want their officers to be able to draw and fire their guns with accuracy, they must provide practice on a pistol range. They know that a skill used only infrequently will deteriorate over time. Similarly, hospitals who need physicians and nurses to be ready for possible emergencies will often conduct regular drills so they can keep skills honed for a possible disasters.