tl;dr:It's common to focus on the practical skills lost when someone leaves. Consider cultural implications too. As a manager, identify a common behavior the employee brought, its impact, and how you want to strengthen it going forward - through your own behaviors, asking someone else, or through the a new hire.
tl;dr:"How do I lead someone who is more experienced than me?" Mark shares 4 strategies (1) Fight the imposter syndrome (2) Realize you're delegating & not supposed to know everything (3) Mention it to the more experienced report & leverage their experience. (4) Learn to coach them.