Mediocrity cannot be remedied, unless you are a big company where you have dedicated departments to cater for these sort of people ( and by the way, they aim to accomplish the same outcome, just a little bit slower and more paperwork). All I am saying is, an employee has no business performing a job he/she cannot do unless he is a trainee with a good attitude. I leave this comment section with one last nugget of wisdom :

There are more skilled and deserving individuals looking for jobs that they can't get because a bad manager is holding on to a mediocre employee.