If you want your children to understand the relentless progression of time and the inevitability of death, get them a puppy or kitten. This way they can see how a living thing grows, matures, reaches its adult prime, starts to fade, completely deteriorates and finally dies, helpfully preparing kids to recognize these stages in their own lives to come.

But if you want to do this without having to clean up poop, just have them watch sports. After all, fans usually first discover athletes when they’re just intriguing prospects and follow them as they become promising young talents and then (occasionally) grow into outright stars before their physical gifts start to fade and they finally wind up pale shadows of themselves, pathetically hanging on before they vanish altogether, usually within a decade of our first hearing about them.

Of course, athletes don’t have to undergo these latter stages: Unlike most living things, they have the option of giving up the game in their prime. Particularly nowadays, when even Timofey Mozgoz can land a $64-million deal, ensuring generations of financially secure Mozgovs to come.

Nico Rosberg has broken the mold, quitting F1 racing just five days after winning his first championship: “I have climbed my mountain, I am on the peak, so this feels right.”

Almost no one actually does give it up early, however. The short list of outliers includes Jim Brown (the NFL’s leading rusher in his final season), John Elway (Super Bowl MVP in his final game) and Sandy Koufax (Cy Young winner in that last year).

Let’s look more closely at them.

Brown had already played nine years and retired only because the Cleveland Browns threatened he would not be paid if he missed training camp to complete delayed shooting on The Dirty Dozen. Brown called their bluff and chose his film career, which kept going long after his gridiron days would have ended regardless.

Elway was 38 and had already played 16 seasons in an era before the NFL created a ton of rules specifically to protect quarterbacks.

Koufax, who had long suffered physical problems from pitching, was told that if he kept going they might literally have to cut his arm off.

In other words, while they were still elite, time was clearly tight for all three and they knew it.

But now Nico Rosberg has broken the mold, quitting Formula One racing just five days after winning his first championship. Only 31, he was one of the two drivers for the Mercedes team. Thanks to current F1 regulations, Mercedes literally is the only make of car capable of competing for the title. Rosberg and teammate Lewis Hamilton have taken the top two spots for the last three years: This season they won 19 out of 21 races between them.

Yet Rosberg announced: “I have climbed my mountain, I am on the peak, so this feels right,” adding that he wants to spend more time with his family. When asked about a future return, he said simply: “No definitely not. End of story. Done.”

In doing so, he’s walking away from a ton of money, since a season as the reigning champ means endorsements galore. Thing is, Rosberg already has a ton of money, having collected a salary of $15.5 million this year alone.

Rosberg is rich, he’s achieved his goal and he still has his health. F1 has gotten much safer but driving at over 200 miles per hour will always have its risks: It’s not so long since the death of 25-year-old French racer Jules Bianchi last summer.

On the other end of the spectrum sits another 31-year-old born, just a few weeks after Rosberg was, New York Jets cornerback Darrelle Revis.

It’s difficult to overstate what, at his peak, Revis meant to Jet fans. We are a franchise that has known much hardship, each loss in recent years made extra bitter by the awareness that Bill Belichick was our head coach for an entire 24 hours before rushing off to New England to wreak havoc on the AFC and all that is decent in this world, as they won titles and we got Butt Fumbles.

Yet we could find solace in one thing: not having to worry about the other team’s best receiver, as he would wind up on Revis Island (trademarked by Darrelle—really), from which there was no return.

In time Revis left New York and eventually—because the universe has a cruel sense of humor—wound up with the Patriots, where naturally he won the Super Bowl.

Revis then made his way home to the Jets and it was just like before, only now he is terrible.

Statistics demonstrate how objectively bad Revis is. So far this season, quarterbacks have thrown to the receiver Revis was defending 58 times. 38 of them, the catch was made. Revis Island is now, at best, Revis Peninsula With Convenient Highway Access. (Trademark pending.)

Darrelle Revis continues to appear in plenty of highlight reels this year: They’re just always of somebody on the other side burning him for a long touchdown.

A lifelong Jets fan, I think the world of Revis. I had the good fortune to interview him some years back and found him to be intelligent, friendly and, most delightfully, approximately my own size. This is rare among NFL players, which is why I will always have a soft spot for Wes Welker. He was, like Ronnie Lott before him and Richard Sherman right now, one of those rare defenders so good at shutting down opposing stars they become stars in their own right.

Revis continues to appear in plenty of highlight reels this year: They’re just always of somebody on the other side burning him for a long touchdown. He is one of the worst players on a three-win team that regularly starts a QB capable of throwing six interceptions in a game.

He is at the point where his own owner is reportedly personally angry with him and a “confidant” allegedly leaked that Revis “doesn’t want to play anymore.”

It doesn’t even matter if these damning reports are accurate: Revis is so bad they could be true. Which is particularly depressing when you remember that just a few shorts years ago, he was regularly making stars look like stooges.

In seemingly the blink of an eye, he has regressed from a standard for excellence to an object of ridicule.

Revis had two moments when he could have gracefully stepped away:

After the 2014 season, when he got that title with the fucking Patriots.

Or even better…

After the 2015 season, when he had returned to the Jets and, while clearly slipping, was still a Pro Bowler.

Had he retired before 2016, he would have already played nine years, the same number Jim Brown did. He’d checked off all the boxes that Hall of Fame voters like to see: Pro Bowls, First Team All-Pro picks, individual awards (he was SI’s defensive player of the year in 2009), that Super Bowl. And he was already ridiculously rich, having earned $16 million in 2015 just in salary.

Of course, Revis didn’t know he had reached his personal mountaintop: Nope, it’s rarely clear you hit a peak until you tumble off of it.

Plus, outsized belief in your own greatness is usually essential to being great. In 2012, Revis suffered a knee injury that required surgery, ending his season. There was no guarantee he would ever be the same player, making it all the more impressive when he earned the Comeback Player of the Year award in 2013 before going on to again be an All-Pro and win that Super Bowl.

Revis must believe that he’s on the verge of making another dramatic return that not only equals past glories, but also lets him reach new heights so lofty that previous peaks seem like valleys. That’s kinda the attitude you need to have to compete at the highest levels of sport. And his former teammate Tom Brady has speculated Revis only needs to get healthy to re-establish Revis Island. So maybe that will happen.

Or maybe, like Willie Mays and George Foreman and Brett Favre and so many other greats before him, his body’s just old and getting older—and the once unbeatable Darrellle Revis will continue giving a generation of young Jets fans a preview of what time will eventually do to them as well…