When I saw that the 59-year-old Pat Summitt, the legendary coach of the Tennessee Volunteers, had officially retired yesterday after 38 years of leading the Vols, I initially was sad that such a legend was having to leave the game so early. But then I did a double take, did some mental math and was blown away: Summitt had been the head coach at Tennessee since she was 22 years old. She was, quite literally, leaving the only job she had ever known.

Consider this: I’m a senior in college and will turn 23 years old in June. I can’t even begin to fathom doing something for the next 38 years of my life. Shoot, I can’t even fathom being 38 years old. But Summitt’s all-too-early retirement made me wonder: how do coaching legends know when it’s time to walk away? How does someone who is so borderline-manically obsessed with a game for so long decide that it’s time to fade into the shadows?

With Summitt, the choice to retire wasn’t really hers to make. Her battle with early-onset Alzheimer’s meant that she was only going to be able to stay on the sideline for so long. But even before Summitt made her diagnosis public, you could tell the end of her career was coming sooner rather than later — at least, to me it seemed that way. I’ll never forget watching her storm up and down the sideline during the 2010 Tennessee-Stanford basketball game in Knoxville. She was icy, intelligent and fearsome in a way that was palpable every time she walked past my seat. But you could also see the bags under her eyes and the hints of weariness when she yelled at all-too-terrified college kids over on the Volunteers’ bench. My dad, who was at the game with me, said she was “like a lion in winter” (the winter of her career, that is). I saw and understood what he meant.

But for other coaching legends, the choice is theirs. And it’s hard to walk away at the right time. Some people walk away on top, like John Wooden, Summitt’s rival for the title of “Greatest College Basketball Coach of All Time”. Wooden hung up his whistle in 1975, after his UCLA Bruins won the NCAA title for the 10th time in 12 years. Others leave in disgrace, like Joe Paterno, whose Penn State program is now sadly synonymous with deceit (and far worse things).

And some coaches just never leave, even when their effectiveness has clearly waned, like basketball coach Larry Brown, who is currently in talks to become the head coach at SMU, one of the most woefully bad college basketball programs in the country.

But back to my original question: How do any of these people even begin to decide when it’s time to leave? Do they do something they never would have done in years past? Do they have a single moment of perfect clarity where they realize they can’t do what they used to do? Does the ghost of Babe Ruth come out of their closet and tell them that “Heroes get remembered, but legends never die,” convincing them that their legacy is safe and they can retire once and for all?

To me, it appears that there are only two things (other than unforeseen circumstances, like in Summitt’s case) that should make coaching legends step down. First, they come to grips with a day when they feel like there’s no challenge left to take on — like there’s no point in chasing the things that you used to desire so much — and they step aside for good. If that day never comes, then the people that the coach trusts, the people who know him or her better than anyone else, must say it’s time to hang it up, instead of an athletic director having to push a coach off the stage in an ugly manner.

Of course, it’s probably not that simple for these coaching legends. After all, when do you think Tara VanDerveer will stop feeling a thrill every time she walks onto the floor at the Final Four? My guess is probably never. Do you think Mark Marquess doesn’t like filling out his lineup card every day? I doubt it. But both of those coaches have slowed considerably in the last few years, and eventually there will come a day when they have to hang it up for good. One can only hope that, unlike Summitt, they get to do it on their own terms — it’s only fitting that they get to choose when to call the final timeout. After all, it’s all they’ve ever known.

Jack Blanchat is on his way to a 38-year stint as managing editor of sports at The Daily. Explain to him what the next 13,750 days will be like for him at blanchat “at” stanford.edu or follow him on Twitter @jmblanchat.