For the record , there's a difference between FIP and pFIP. FIP, itself, isn't predictive. It tells us what a pitcher's performance was as best a stat can (way better than ERA, for example). 'FIP is a measurement of a pitcher’s performance that strips out the role of defense, luck, and sequencing, making it a more stable indicator of how a pitcher actually performed over a given period of time than a runs allowed based statistic that would be highly dependent on the quality of defense played behind him, for example. Certain pitchers have shown an ability to consistently post lower ERAs than their FIP suggests, but overall FIP captures most pitchers’ true performance quite well. For this reason, FanGraphs’ version of Wins Above Replacement (WAR) for pitchers is based on FIP rather than on ERA and even analysts who prefer a different method of determining WAR find FIP to be extremely useful and informative.' pFIP is from hardball times and it attempts to be a predictive version of FIP, using different weights and giving certain aspects, like strikeouts, more weight. 'The weighting of FIP that is supposed to work as a describer puts the lowest weight on strikeouts, but strikeouts by themselves are the most predictive statistic. pFiP attempts to account for this fact by giving strikeouts more weight. The way FIP works as it stands is a much better describer than this statistic would be, but my goal is prediction, not description.