by Max Mulitz
The best way to measure a receivers total value is some version of Net Expected Points (NEP) or Expected Points Added. These models basically take the expected point value of the down and distance situation after a play where the receiver was targeted and then subtracts the expected point value before the play. For example a 10 yard reception on 3rd and 15 at a teams own 25 would have a slightly negative value as the team would usually be forced to punt, as would an incompletion. A 20 yard reception would have a high positive value as 3rd and 15 at your own 25 is significantly less valuable than 1st and 10 at your own 45 in terms of expected points. For more on how Net Expected Points are calculated click the links above.
Why Use Expected Points instead of other Metrics
The benefit of expected points compared to other receiver metrics like yards per target or catch rate is that expected points maps directly to wins and therefore could eventually allow us to meaningfully compare players across positions. Contrast this with Yards per Target or Catch Rate, which would need to be converted into a universal metric before any sort of comparison between receivers and say, Linebackers could be made. Because scoring points is the ultimate goal of football, expected points added is universal in a way other receiving statistics are not.
Another benefit of expected points is that it answers the question “when player x was thrown the ball, did good things happen?” It is possible to have a low yards per reception and still be a valuable receiver, a player like Wes Welker who ran the vast majority of his routes near the line of scrimmage and had an excellent catch rate is an example. On the other extreme, Vincent Jackson had poor catch rate most of his career because he ran primarily deep routes (which are completed less often) but his huge production on his receptions still allowed him to become an elite performer. Expected Points isn’t flexible, if a player has very poor expected points per target it means when they were thrown the ball good things didn’t happen and if the player has high expected points it means that when they were thrown the ball good things did happen on the whole. A metric like Yards Per Target, which combines yards per catch and catch rate, does a much better job of measuring a receiver’s ability than simple catch rate, but there’s no reason to believe an 18 Yards Per Catch Receiver with a 50% Catch Rate (9 Yards Per Target) and a 12 Yards Per Catch Receiver with a 75% catch rate (9 Yards Per Target) are necessarily equally valuable. It is necessarily the case however that if two players receive equal targets and each produce 20 Net Expected Points then they did in fact get equal production out of their targets.
Weaknesses and Limitations of Expected Points
Net Expected Points tells us if good things happened when a receiver was targeted. They do not tell us how responsible the receiver is for that benefit. Targets coming from Aaron Rodgers are likely to be more accurate (and therefore valuable) than targets from a career backup QB. Some of this can be alleviated by adjusting Expected Points for quarterback by comparing to how the Quarterback does throwing to other receivers, but this method would underestimate receivers with excellent teammates and would overestimate players with very poor teammates.
Expected Points also don’t tell us what happened when a player is not targeted on a play. For instance, if a player fails to get separation all game and is only targeted once on forty routes, where he coverts a 3rd & 3 by gaining 7 yards, his Net Expected Points for the game will be positive, in spite of the fact that he clearly hurt his team during the game by consistently failing to become open.
On every pass play there is some risk of a sack, which is a negative result, but plays where a receiver is targeted obviously are never sacks, so by only looking at pass plays where a receiver is targeted we are ignoring some of the inherent risk in deciding to pass the ball. By subtracting a players NEP/Target from the average for players at their position (for receivers the average is right around .6 most years) and then multiplying by total number of targets, we can get a better sense of the players value relative to the average player.
Another issue is Net Expected Points doesn’t account for route quality or tell us anything about player style. A receiver who runs the highest value routes and is regularly targeted downfield may have greater opportunity to return value than a player who only runs short routes near the line of scrimmage, but the short route player may be outperforming how the types of targets they receive by a greater amount. Expected Points doesn’t tell us anything about the types of routes a receiver is asked to run.
Net Expected Points also doesn’t measure a receivers blocking ability or soft skills (running pick routes well to help teammates get open and drawing safety help, for example.)
Because of these failings, Expected Points do not, by themselves, predict how a player would do in a different system or with different usage than they have received. This problem is endemic to all box score metric, which can only measure what actually happened, not what might have happened had a player been used differently.
Expected Points tells us the value of what happened when a receiver was targeted, though it is not the end-all-be-all of receiver quality. Expected Points benefits from being a universal metric, that is, if done correctly it would allow us to accurately compare players across positions. Expected Points can be adjusted to account for certain aspects of a players situation, though these adjustments are imperfect.
While other metrics may be necessary to supplement expected points in order to understand a receivers particular talents and abilities, some version of expected points (possibly transformed for situation or role) should be the foundational Key Performance Indicator for evaluating the value of a receivers’ contribution.