The Limits of a Projections System
How accurate can a projection system be?
Tango Tiger asked this question earlier this year, and his answer was 0.73
Pecota actually beat this for the hitters in my sample this year (.736), although that could be explained by random variation, we know that a projection, no matter how sophisticated, would be able to consistently beat a person or divine entity who knew, exactly, what a player's true ability was.
How can we go beyond the theoretical approach and test how accurate "perfect" projections can be? You'd have to be a Baseball God. It just so happens that to the players of the APBA Major and Superior Leagues, I am the Creator. In 1982, I said, "Let there be baseball" And there was baseball. And I saw it was good.
25 years later, my league has 30 teams. I tried the same test for my league that I put all the other projection systems through, minimum of 500 at bats, correlation of OPS. The result was r = .770.
I've only looked at one year, but if that holds up, that is our limit.