I have explored this quite a bit, but short of making it a crusade, I want to invite you to share your opinion with one of the most respected statisticians working in football, Brian Burke. He asks:
Here's a question. I've been applying the Win Probability model and Expected Points model to individual player performance lately. For QBs, it's fairly straightforward--we add up all the successful events like completions and touchdowns, and subtract out all the unsuccessful events like incompletions and turnovers. But what about receivers? Should we count incompletions and interceptions against them?
People know my opinion about applying stats to specific players. I would argue even applying stats to quarterbacks is futile, as its attempting to create a universal measure across completely different offenses with different abilities and different schemes, and especially difficult because unlike baseball, a single in the ninth inning of a blowout is not as easy as a single in the first inning of a scoreless game. A completion when a team has nothing to lose by allowing it, say in the final five minutes of a thirty point blow out, is much easier than a completion in the last minute of the third in a one score game. The achievement is superficially the same, but the game state and game conditions are completely different. And the game state and conditions impact the pass rush and coverage schemes, along with the players that populate those schemes, their effort and their decision making.
Regarding Brian's specific question, I think it's better to include all information and produce a stat that measures "targets to that receiver" rather than the receiver himself. That measure is not possible with the information currently provided by the NFL, and truly, is not maybe possible given the information we will ever have.