Mariano Rivera is perhaps the most revered player in the majors today, as well as the oldest, so before this season began you had to be slightly afraid for him. Who would want to see a pitcher who's been so nearly perfect for so long in diminished form? The idea of it could make you cringe.

As if to impart some final lesson in his final tour, Rivera has spent the first five weeks of the year pitching exactly as well as he always has. (Career ERA coming into the year: 2.21; 2013 ERA going into Sunday's game: 2.19.) Open him up, it seems, and you'd get nothing but wires and gears. If, after his final game, he were to announce that he is in fact an advanced defense project, a human drone, no one would be surprised, and he'd be elected to the Hall of Fame on the first ballot anyway. Everyone would acknowledge that while the situation is unusual, it isn't his fault that he was made and not born.

Everybody knows about Mariano Rivera's dominance—but the root of his success has been his ability to adapt over the years. Getty Images

That he's doing this at all at 43, let alone coming off a freak knee injury that cost him a year, is even more outlandish than you might think. While it hasn't been rare for elderly starters to take their turns over the last 30 years, just five relievers have pitched 10 or more innings at Rivera's age. Only one, the mostly forgotten Doug Jones, pitched well, and with a 3.93 ERA he wasn't remotely close to Rivera's class. The man is now, as he always has been, utterly unique.

The best illustration of this might be his best pitch, the famous cutter he throws around 90% of the time. Casual attention suggests it's just the same as it's always been—perhaps a bit slower, but still running like a chain saw and darting around in ways that shouldn't really be possible, especially for such a heavy pitch.

According to data from Pitch F/X, a camera system installed in each big-league park that tracks the speed and trajectory of every pitch, this is actually true. His cutter is coming in at 90.8 miles per hour this year, down from 92.2 two years ago, but moving slightly differently—8.2 inches vertically and 2.2 horizontally, as opposed to 7.4 and 2.5 in 2011. In other words, Rivera has been able to compensate for speed with motion, remaining just as effective all the while.

This isn't normal. For obvious reasons there aren't many pitchers to whom to compare Rivera, but the few who have pitched in their 40s during the seven years for which Pitch F/X data is available haven't shown any tendency to add movement as they've aged. At 41, for example, when Trevor Hoffman was brilliant, his fastball moved 12.3 inches vertically and negative 1.3 horizontally; at 42, when he was awful, those numbers were 11.7 and -1.9; at 43, he was out of the game.

Not too much should be made of this—the relationships between speed, movement and effectiveness are complicated and mysterious, and the small margins here give a hint as to why old salts have always claimed baseball is a game of inches. It is, though, a view on Rivera's particular genius, and how the key to his unnatural consistency has always been his willingness to accept change.

It may be that few remember it now, but Rivera didn't throw his famous cutter when he first came to the majors, and he didn't throw it for his first couple of years as a reliever, during which he was as good as he's always been. In those years, in fact, his main pitch was a hard, high fastball that seemed to burst out of his hand and run up toward the top of the strike zone, the precise opposite of a cutter.

This sort of thing runs through his whole career. A fly-ball pitcher at the beginning of his career, he spent most of his eternal prime inducing grounders until, over the past few years, he no longer did. He has struck out as few as 15% and as many as 31% of the batters he has faced in different years. He has had years where a quarter of the balls put in play against him were line drives, and years in which fewer than 10% were. Over the years, everything has changed but the results.

You can draw whatever life lessons you like from that, but the main thing is clear: No one should ever be afraid for Mariano Rivera, and if by some chance he decides to come back for another year, he'll devise some way to make it another nearly perfect one.

Write to Tim Marchman at