How many times have you heard analysts refer to the NFL as “a passing league” in recent years? At first glance, that axiom certainly appears to be true. Pass attempts, passing yardage, touchdown passes, and passer rating are all at their highest levels in history and this trend shows no signs of slowing down. However, today’s passing games are also more conservative and horizontal than at any point in NFL history. As completion percentage continues to rise, the average length of those completions is dropping just as quickly. The chart below shows the relationship between completion % and air yards per completion since 1992 (that’s when air yards started being tracked):
As you can see, completion percentage has risen steadily in recent years, but it’s come at the cost of throwing downfield. The passes in today’s NFL are significantly shorter than they were even 10 years ago. I included week 1 of the 2015 season for comparison’s sake, and it stands out like a sore thumb. The average length of completion has absolutely fallen off a cliff so far this year. Now, it’s highly probable that this will regress toward the levels of recent seasons, but also fairly likely that 2015 will end up being the most conservative passing season in NFL history.
Another way of measuring passing style is to separate yardage into air yards and YAC (yards after catch), then calculate the percentage of total passing yards that came through the air. I call this Air %. Not surprisingly, Air % is trending downward as teams attempt shorter and shorter passes. Interestingly, overall yards per attempt has actually risen slightly during this timeframe, indicating that YAC has increased even faster than air yards have decreased.
Over the last couple seasons, the league has inched closer to a 50/50 balance between air yards and YAC. But once again, week 1 of the current season shows an acceleration of this downward trend. Teams actually compiled more yards via YAC than via air yards. Frankly, I find this remarkable. Apparently, teams have decided to exploit today’s favorable passing rules by throwing short passes and letting their receivers run free for extra yards after the catch. Interestingly, when the illegal contact rules were re-emphasized back in 2004, we saw the exact opposite effect; quarterbacks threw deeper and receivers gained fewer YAC. It will be fascinating to see if defenses figure out how to combat the short passing game, or if this trend will continue on into the foreseeable future.
In official statistics, air yardage and YAC are combined into one total. This can be very misleading for QB’s at either end of the spectrum, so I think it’s important to measure how QB’s gained their yards. In week 1, there were 16 quarterbacks who padded their stats with more YAC than air yards. Drew Brees was the biggest culprit, as only 20.3% of his passing yards came through the air against the Cardinals. How does this happen? Well, Brees had the two longest completions in week 1 (59 and 63 yards), but both completions happened at the line of scrimmage with nearly all of the yardage being gained after the catch. Matthew Stafford and Philip Rivers played in the same game, and both saw the vast majority of their yards come after the catch. This chart shows those 16 quarterbacks from week 1 who posted an Air % below 50.
Generally speaking, it’s fair to attribute air yards primarily to the QB and YAC primarily to the receiver, so splitting the yardage up can provide a good estimate of how much the QB carried his passing game compared to his receivers. Obviously there’s plenty of overlap, as quarterbacks certainly have some influence on YAC and vice versa. There is no end-all-be-all statistic in football, but I believe these numbers are useful in adding just a little more clarity to the picture.