If you have expertise or experience you should be able to complete a task in an acceptable way.  The better your skill or experience the greater the efficiency or quality.

For example if you have both training and practical experience you can probably perform a plumbing repair more quickly and with less risk than I could, I am not greatly experienced in plumbing.

This is not to say I can’t do plumbing work (in fact I have on a number of occassions) but it has seldom been fast and when problems were encountered I have needed help.

Capability

In the plumbing example, while I do not have extensive skills and experience with plumbing I am capable of doing the job. The extent to which I have the power and willingness to complete a task is my capability.

Selecting Leaders, Group/Team or team members

If you are interesting in a winning combination, when building a team   (sports or otherwise) a business or other organization the mix of skill and ability is critical.

Unfortunately there is no absolutely correct mix of skill and capability.   The best balance varies widely depending on numerous factors.

These include the nature of the role, the overall complexity of the activities, envionmental factors and well, just about everything else.

The key is recognizing that the balance between skill and ability needed in any given situation varies and should be analyzed and determined before selecting someone to tale on the assignment.

This is not an easy task but a very worthwhile one which increases your chance of selecting the best resource for any given role.