Your coaching should not only aim to understand why there is a performance gap, but also to help the employee understand. You do this by asking questions about their thoughts. This allows you, as coach, to recognize the thought process that is driving the lack of results. Helping employees understand why there is a performance gap is an important part of coaching.
Good coaching always involves getting the employee engaged in the process of finding a solution. Their willingness to engage creates the environment in which change can take place.
One aim of coaching is to help the employee own responsibility for filling the performance gap. The manager is there to support and help, but part of that help comes in calling the employee to be accountable for fulfilling the requirements of their job.