Before the expert leaves: a guide to transferring critical knowledge through mentoring

When an experienced expert retires or moves to another role, more than one person leaves the organization. Years of accumulated intuition, relationships and knowledge of exceptions go with them. This guide explains how to use mentoring as a tool for transferring that knowledge to a successor in a planned way.

A big problem, weak preparation

APQC’s “Great Retirement” report, published in 2025, shows the scale of the problem clearly. According to the report, only 8 percent of surveyed organizations consistently capture the knowledge of departing employees, and 16 percent don’t try at all. The report lists lack of time, resources and senior leadership support as the main obstacles.

The issue isn’t new, either. A 2005 T+D article drawing on David DeLong’s work recalls that much of the Apollo program’s knowledge was lost along with the engineers who retired. According to DeLong, the first job is to identify which knowledge is actually at risk.

Tacit versus explicit knowledge

Ikujiro Nonaka’s knowledge creation model is a good starting point for choosing a transfer method. Nonaka distinguishes two kinds of knowledge:

• Explicit knowledge: Knowledge that can be written down, documented and stored in a system. Procedures, technical specifications, customer lists.
• Tacit knowledge: Knowledge embedded in a person’s experience that’s hard to put into words. Recognizing a fault by its sound, sensing a customer’s real objection, knowing whom to call in a crisis.

According to Nonaka, tacit knowledge passes from one person to another mostly through shared experience and direct interaction. Making tacit knowledge explicit usually happens through dialogue. DeLong also stresses that the method has to fit the type of knowledge: training suits explicit knowledge, while storytelling and after-action reviews suit tacit knowledge better.

Dorothy Leonard and Walter Swap’s “Deep Smarts” work reaches the same point: experience-based expertise develops through guided experience and coaching relationships. That’s why mentoring is central to this work.

Step 1: Identify the knowledge at risk

For each expert who will leave, ask these four questions:

1. Criticality: Which decision, process or customer is affected if this knowledge is missing?
2. Uniqueness: Who else has this knowledge?
3. Tacitness: How much of the knowledge is written down, and how much lives in the person’s head?
4. Timing: When is the expert leaving, and when does the successor need to be ready?

Topics high in both criticality and uniqueness come first. In the TechnipFMC example reported by APQC, each departing expert is treated as a separate project. Interviews and a risk assessment come first; then a transfer plan is built, starting with the biggest gaps.

Step 2: Choose the right methods

No single method is enough for tacit knowledge. Use these together:

• Shadowing: The successor watches the expert inside real work. Each shadowing day closes with a short Q&A: “Why did you do that? What were you looking at?”
• Learning by doing: The roles flip. The successor does the work, the expert watches and gives feedback at the end. Start with low-risk cases, then move to harder ones.
• Decision log: For important decisions, the expert writes short notes on what they knew, what they assumed and what they expected. The successor reads the notes and prepares questions. This makes judgment visible.
• After-action review: Developed in the US Army, this method compares what was planned with what actually happened and identifies what to keep and what to change. A 20–30 minute review after each critical task or event is enough.
• Stories and cases: The expert walks through difficult past cases. The successor turns them into short case notes.
• Relationship handover: The expert introduces the successor to key internal and external stakeholders in joint meetings.

Questions that surface tacit knowledge

Experts often don’t know what they know; they just do the work “the way it’s done.” In mentoring sessions, questions like these from the successor make that knowledge visible:

• “What’s the first thing you look at in this situation? What would worry you if you saw it?”
• “Can you describe a case where the rule didn’t work?”
• “What mistake does a newcomer make most often here?”
• “Whose view do you get when making this decision, and why?”

The successor takes notes on the answers and, in the next session, reads them back to the expert in their own words. The expert corrects them and fills in what’s missing.

Step 3: Write the transfer plan

A one-page plan is enough for each expert–successor pair:

Knowledge area	Risk (criticality / uniqueness)	Knowledge type	Method	Target date	Readiness measure
Annual budget negotiation	High / High	Tacit	Shadowing, decision log	Month 4	Successor runs one negotiation under the expert’s supervision
Line fault diagnosis	High / Medium	Tacit	Learning by doing, after-action review	Month 6	Independently diagnoses 4 of the last 5 faults
Supplier relationships	Medium / High	Tacit	Relationship handover	Month 3	Introductions to key suppliers are complete
Quality procedures	Medium / Low	Explicit	Document update, training	Month 2	Procedures are current and approved

Timeline

An example framework starting 9–12 months before the departure:

1. Months 0–1: Risk assessment, choosing the successor, approving the plan.
2. Months 2–4: A period focused on shadowing and the decision log. Explicit knowledge is documented.
3. Months 5–8: Learning by doing. The successor takes on responsibility step by step, and the expert steps back.
4. Months 9–12: The successor works independently, and the expert becomes someone to consult. A closing review is held.

If time is short, narrow the scope; focus first on the two or three highest-risk areas.

Measure whether the successor is ready

Answer “Are they ready?” with a shared scale for each knowledge area, not with gut feeling:

• Level 1: Has observed and can describe the steps.
• Level 2: Can do it with the expert alongside.
• Level 3: Can do it independently; consults the expert only on exceptions.
• Level 4: Can teach it to someone else and handle the unexpected.

Have the expert, the successor and the manager each rate separately. The gaps between their scores show where more work is needed. The plan can be considered complete when most critical areas reach Level 3.

Don’t forget culture

DeLong stresses that mentoring-based transfer requires an organizational culture that values teaching, and that competitive cultures that treat knowledge as power undermine the effort. Make the departing expert’s contribution visible, add the transfer to their job description and free up time for it.

When identifying successor candidates, take a look at the High Potentials program; when planning development steps, see the career path tool.

Sources

• Navigating the Great Retirement with KM & AI (APQC, 2025) — Knowledge capture rates, obstacles and TechnipFMC’s expert-by-expert transfer process.
• The New Brain Drain (Jennifer J. Salopek, T+D, 2005) — DeLong on identifying risk, matching methods to knowledge types, and his warning about culture.
• A summary of Nonaka’s knowledge creation model (Bill Spencer) — The four modes of conversion between tacit and explicit knowledge.
• Deep Smarts (Leonard and Swap) — How experience-based expertise develops through guided experience and coaching.
• After-action review (Wikipedia) — The origin and core logic of the after-action review.