Here is a brief excerpt from an article by Jeff Weiner for LinkedIn Pulse. To read the complete article, check out others, and sign up for email alerts, please click here.

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In a previous post, I wrote about five tools to look for when recruiting superstar talent. In this post, I’d like to share some key lessons learned over the years when it comes to retaining your top people.

As a general rule, it’s important to note that by the time your best talent comes to you and says they’re leaving, more often than not, it’s too late. They’ve long since reached the conclusion it’s time to go, having repeatedly seen or experienced examples of why they no longer want to be at the company. At that point, it’s going to be extremely difficult to keep them.

One of the reasons it’s so hard to change a person’s mind once they’ve communicated their intention to leave is that they may not be willing to share the truth behind their rationale. At least in the case of the tech industry, it’s a “small town,” so people understandably want to leave doors open vs. burning bridges by speaking hard truths. Without knowing what’s really motivating a person’s decision to transition, it can be challenging to convince them otherwise.

Additionally, if losing the person to another company, you’ll most likely be up against a grass-is-greener dynamic. Departing employees know what it’s like at your company — both the good and the bad — but they are being wined and dined by hiring managers and recruiters who are telling them only the good, if not the great, about what it’s going to be like to join a new team.

Lastly, sometimes the person can’t quite put their finger on the reason they want to make a change. They just “know it’s time” or have a gut feeling it’s the right thing to do. Generally speaking, it’s hard to counter an argument when one isn’t being made.

All of this underlies one critical dynamic when retaining talent: Start the retention process when the person is still open to staying and not after they’ve already told you they’re leaving. From time to time, you may be fortunate enough to walk someone back from the ledge (in certain cases, I’ve seen people retained even after they’ve accepted roles elsewhere), but this is the exception rather than the rule. If you are counting on your ability to persuade people to stay after they’ve already made the decision to leave, you should expect to lose far more talent than you save.

So how can you prevent this scenario to begin with? In my experience, there are three critical must-haves, all of which need to be in place well before the individual comes to you saying they are on their way out: Mentorship, career path, and recognition.

[Here’s the first critical must-have.]

Mentorship

The primary role of a mentor in this case is to help the mentee determine what it is they ultimately want to do, and ensure they are well equipped to pursue that path. Why is this so important when it comes to retention? Because the clearer your talent is about their desired end goal, the earlier in the process you can work with them to make it a reality.

Bear in mind, simply because you are someone’s boss, doesn’t make you their mentor. To the contrary, by virtue of your role as manager, your employee may be hesitant to share their future plans (especially if it doesn’t include you), or concerns about why working for you or your team is leaving them dissatisfied. Without knowing what’s on their mind, it’s going to prove prohibitively difficult to make the appropriate course corrections.

Rather than assume you are the right mentor for your directs, help them find the right mentor. That means leveraging your understanding of the individual — their strengths, weaknesses, values, sensibilities — and suggesting the best person to complement them. A mentor can come from within your organization or outside the company. Either way, they are there for your employee first, providing an impartial sounding board that can draw upon the mentor’s own relevant experiences to assist the talent in making and pursuing the right career choices.

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Here’s a direct link to the complete article.

Jeff Weiner is CEO at LinkedIn. Previously: Accel Partners, Greylock, and Yahoo! He is a graduate of the Wharton School at the University of Pennsylvania.