If you aren’t member over at Baseball Prospectus, you really are missing out, but I’m not trying to sell anything here, and in fact, this content is 100% free. Nate Silver, the most prominent figure at BP, wrote an “unfiltered” blog entry today, touching on the popular phrase “TINSTAAPP”, also known as “There Is No Such Thing As A Pitching Prospect”, and how relevant it is. This was the most interesting part of the article
One thing that distinguishes young hitters from young pitchers is that young hitters can pretty much count on making steady improvements from the time they start playing professional ball until the time they’re 26 or 27. You might have a guy like Cameron Maybin who would be pretty overwhelmed if he tried to play in the major leagues today — but we can be fairly certain that he’ll be able to handle the big leagues in two or three years time. Cameron Maybin is a prospect.
The same is not the case with pitching prospects. Although there are a few categories of pitching prospects — particularly guys with good stuff, high strikeout rates and highish walk rates (think Homer Bailey) — that tend to improve more often than not, in general there is no systematic pattern of improvement after the age of 21 or so. Sometimes guys get better, of course, and sometimes they do so in a hurry — but you can’t take a young pitcher in a vacuum and expect him to improve the same way that you can for a hitting prospect. Mark Rogers (to pick on some low-hanging fruit) will probably never get his command sorted out, Yusemiro Petit will never add enough ticks to his fastball to become a useful major league starter, Gavin Floyd will never learn how to keep the ball down, and so forth. All of these things are possible — but they’re not very likely.
This strikes me as being a very interesting area of study. Do pitchers really not drastically improve after the age of 21, for the most part? If you disagree with this notion, I’d love to see some data to illustrate the point. I may work on this as a project at some point down the line.