The use of statistics in football is a source of great controversy. Much debate exists as to whether numbers are used properly. Is there any one stat that you think is underutilized?
For me, it is yards per attempt at the quarterback position. When it comes to quarterback play, people frequently talk about completion percentage, touchdowns, interceptions, yards, and quarterback rating. I think yards per attempt might be the best gauge of pure efficiency, though.
Touchdowns, interceptions, and yardage have their uses, but they are volume stats. Players on teams that throw more will see higher totals. Completion percentage can tell us about accuracy to a certain extent, but not all passes are equal in difficulty. Some teams throw down the field more than others. A quarterback might have a lower completion percentage, but he also might be throwing more difficult passes.
I think yards per attempt does a nice job balancing things. A quarterback might have a high completion percentage, but if he is checking down for three yards too frequently, he isn't very efficient. On the other hand, a quarterback might not have a super high completion percentage, but if he is frequently hitting on big plays, he might be more effective than some of the numbers would indicate. A player with a high yards per attempt number is likely hitting on his share of big plays but still knows when to check down and take something when nothing is available down the field.
Is there any statistic you think is underrated?