Leader beware. One of the most dangerous employees in the organization is that person that is almost good enough for the job. The problem is exacerbated if this person is likable and especially loyal. This convergence of traits traps the leader into a state of unintentional procrastination.
This person must be removed. Perhaps there is another role for them. If not, they must be removed entirely. It takes courage and decisiveness but the leader who fails to identify the near-miss will consign his organization to mediocrity.