If your business can afford this, talk and give him/her 1-3 months to reach the level you need, sort of a probation. It doesn't need to be public and shame, jus

If your business can afford this, talk and give him/her 1-3 months to reach the level you need, sort of a probation. It doesn't need to be public and shame, just make your case clearly and frankly, face to face. If talk derails, offer severance for resignation. Worst case, cut it short, lose a friend and fire, but from your op I don't think it will end this way.