A basic study of 'peak' years

First, how to define 'Peak'? It's a players most productive seasons, but how many? Their best three, four, five? To have a nice simple number, I'll choose five. Using BRef's Play Index, I'll look at various age ranges, e.g. 24-28, 25-29, 26-30, etc. Then I'll take the average runs created for the top five players, followed by the 10th, 20th, 30th, 40th and 50th player. I'm going to try looking at the modern era, so I'll go from 1973 (start of the DH) to the present. First, hitters overall, to be followed by LHB and RHB. Then the same for pitchers.

Overall, hitters are easier to analyze. Their peaks have a nice, simple bell curve. In 5-year spans, they peak from 27 to 31 (you could also expand it a bit from 26-32). Going by 3-year spans, hitters peak from 27 to 29 (while still hitting great at 30 and 31). What about the difference between lefties and righties? Righties peak relatively early - 25 to 29. Lefties peak a bit later - 27 to 31.

Pitchers are pretty similar, peaking at the same ages as hitters - 27 to 31. However, if the peak was to be extended two years, it would definitely include the age 25 and 26 seasons. In other words, pitchers peak slightly earlier than hitters. A problem comes when differentiating between lefties and righties. Southpaws peak from 24 to 28. Righties peak from 27 to 31 - that's a fairly significant difference.

Interesting the difference in handedness. Lefty pitchers peak earlier than righties, but lefty hitters peak later than righties.

What does all this tell us?
- Well, in terms of current events, the Yanks should be very careful trading for Johan Santana. He's a small lefty that may have peaked early (not uncommon for southpaws) and is on the way down. Randy Johnson and Tom Glavine are outliers.
- It may still be a few years before Robbie Cano hits his prime and becomes the #3 hitter many think is inevitable. Be patient.
- Arod is on the way down.
- Melky should only get better.
- Same with Hughes, Joba and Kennedy.