Well somebody took the time to look at each of those plays and watched only what Crockett was doing on each one, and gave him a grade on his performance. Then another person that was also fixated on Crockett, watched all of his plays and gave him a grade. They then came together, looked at each others notes and gave him the final grade for the game. It doesn't mean Crockett is a bad player, it just means that for those seven plays where he was on the field (mostly were blocking plays) he made more mistakes than he had positive plays. But i see what you are saying. When you have such a small sample size it is difficult to pass judgement on a player based solely on a handful of plays. I mean if he finished the game, the grade would be totally different (probably in the plus category) because it would be taking into consideration a larger amount of plays. I wouldn't discount PFF as a tool to measure a players success though. Really the best barometer of a players success is given at the end of the year. This number totals up all of the game grades and gives the player a grade for the season. The larger sample size and all of the data that is contained in this final number is one of the best ways to evaluate a players success.