Then according to Chris Carpenter's "past performances", http://www.baseball-reference.com/c/carpech01.shtml he would had continue to be a talented, but crappy pitchers. "Past performances" is not the best predictor, because doesn't take into account different variables. It's a definition. You cannot predict by things that have not happened yet. I think what you mean is that there are things beyond stats that can be used to predict, but those are most assuredly still past performance. There is quite literally nothing aside from past performance and wholely irrational beliefs that can be used to predict future performance upside? tools? makeup? what do your base them on? your crazy imagination, or his past performance? What if you're a scout, and a guy has great past numbers, but you go out and see him play somewhere and talk to him and it becomes painfully obvious the man has suffered a mental collapse? Do you still sign him because of his past performance? Or let's say there's a guy who has been pretty mediocre all his minor league career, and you visit him, ask him to get an eye test and he comes back with 20/200 vision? Do you write him off because of past performance?