Last week, we looked at plus-minus catch rates for wide receivers -- and in the process, which wideouts were likely to see their performances (on-field and fantasy) shift positively or negatively.
Of course, catching the ball is only part of a receiver's job, which leads to the second statistic we've recently developed to measure performance: YAC-plus, or, logically, yards after catch-plus. The process for finding a player's YAC-plus is similar to that of plus-minus (detailed on the above link), but it focuses on how a player does after he catches the ball, as opposed to his ability to catch passes.
For every completed pass, we establish a baseline value of YAC by looking at the average gain on similar passes over the past four seasons. A pass thrown eight yards downfield on second-and-10 to the left side of the field, for example, accrues an average of 3.2 YAC. (Unlike plus-minus, these figures are per completion, not per attempt.) If a player catches such a pass and runs for six yards after the catch, he's picked up 2.8 YAC-plus. If he doesn't gain any yards after the catch, he's at a YAC-plus value of minus-3.2 YAC; admittedly that's confusing -- that you can have a 'YAC-plus' value in the minus category -- but it refers to a receiver's ability to make more happen once he hauls in the pass.
You can read more about the YAC-plus concept here, as well.
One of the things we found in studying YAC-plus is that it's not very consistent from year-to-year; for qualifying receivers, there's a year-to-year correlation ranging from .17 (2007-08) to .44 (2006-07), which is a range of "just about useless" to "adequate" as far as predicative value goes. With only four years of data, YAC-plus is a work in progress, but there are still some aspects of receiver performance in 2009 that we can safely say will change in 2010. That includes a decline -- or an improvement -- in the performance of some notable fantasy names.
Note that all mentions of YAC-plus below are on a per-catch basis; a player that has a YAC-plus of 1.5 gained, on average, 1.5 yards more than a league-average player would have given the same completions.