Pro Football Focus
Pro Football Focus (also written as ProFootballFocus, and often referred to by its initials, PFF) is a website that focuses on thorough analysis of the National Football League (NFL) and NCAA Division-I football in the United States. Beyond posting the standard NFL statistics for evaluating players, PFF produces numerical grades for teams and players by watching and grading every player on every play.
PFF was founded by Neil Hornsby in the United Kingdom. Dissatisfied with some limitations of standard statistics, Hornsby began grading players in 2004. The staff gradually expanded over next few years, and the site was launched in 2007. The 2007 NFL season is the first season for which PFF has complete data. For the 2011 season, PFF provided customized data to three NFL teams, agents, media and NFL players. In 2014, sports commentator and former NFL player Cris Collinsworth bought a majority interest in the service, which moved its operations to Cincinnati, where Collinsworth resides.  PFF began collecting data for every NCAA Division-I college football game in 2014.
PFF grades every NFL player's every play on a scale of -2 to +2 using half point increments. The grades are based on context and performance. A 4-yard run that gains a first down after two broken tackles will receive a better grade than a 4-yard run on third-and-5, where the ball carrier does nothing more than expected. A quarterback who makes a good pass that a receiver tips into the arms of a defender will not negatively affect the quarterback's grade on that play, despite the overall negative result for the team.
Furthermore, grades are separated by play type. Beyond just an overall grade, an offensive lineman receives one grade for pass-blocking and one for run-blocking. The average grade is meant to be zero, and raw grades are normalized.
In watching every game, PFF is also able to record information and create data that is typically unavailable. One example is how frequently individual offensive linemen yield pressure.
PFF has been criticized by the analytics community regarding the accuracy and veracity of its ratings. In contrast to the purely quantitative ratings released by sources like Football Outsiders, TeamRankings, and numberFire, PFF uses qualitative and opinion-based grading as the root of their ratings. As such, the ratings are not truly quantitative and could be seen as being prone to bias, poor sample sizing, or other issues.
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