I think that we will all agree that at your workplace it is important how the tasks are performed, not who performs them. We can though disassemble “How” into many little building blocks, such as speed, efficiency, confirmation to rules, accuracy, consistency, professionalism and whatever you can come up with. From here is just a little step towards personal properties of various workers. We all know, that generally women are more exact and patient when it comes to quality control or hand painting. Patience and accuracy are just two of our building blocks. Find more and fit them to a person in your organisation and you will end up with a match which could yield the best results for you. For this though you should take your time and observe your people.
One consequence of the above thought is that simply loosing a worker and replacing it with another for the same job carries a certain risk with itself. You can never be sure that this new person will do a better job, especially if the worker you lost went away on its own because organization failed to properly manage that relationship, not mentioning the fact that the “how blocks” are unknown in new person and have to be first discovered.
Another consequence is that you can find the job for a person or a person for the job. Takes patience, knowledge of what needs to be done and how (very important); and knowledge of your people.