Sunday, November 28, 2010

The Statistics of Football: Punts versus Field Goals

While watching some (American) football this afternoon, it hit me how strangely kicking performance is measured. Punting and place-kicking are measured differently when tallying the statistics of the kicker. As far as I can tell, there is no good reason for it. More on this at the end of this post. First some background (skip to the regular-sized font if you need no introduction to punting and place kicking).

When punting, the kicker stands 15 yards behind the line of scrimmage (spot of the ball). From that spot on the field, the kicker drop kicks the ball high in the air -- and far down the field -- to the other team. This
punt transfers possession to the other team at the point where the other team fields (and returns) the ball.

For official statistics, the length of the punt is recorded as the distance from the line of scrimmage to wherever the ball is fielded (or stops rolling). Consider a couple of examples:
1. The line of scrimmage is at the team's own 20 yard line. The punter kicks from the 5 yard line. The ball travels to the other team's 35 yard line (passing own-30, own-40, 50, other-40) where the ball is caught by the other team and returned to the 50 yard line. This is a 45-yard punt because there are 45 yards between the own-20 and the other-35.
2. The line of scrimmage is at the team's own 45 yard line. The punter kicks from the 30 yard line. The ball travels in the air to the other team's 6 yard line, but then bounces to the 2 yard line where it comes to rest. This is a 53-yard punt because there are 53 yards from the line of scrimmage and the point where the ball rested, but was not returned.
3. The line of scrimmage is at the team's own 45 yard line. The punter kicks from the 30 yard line. The ball travels in the air to the other team's 6 yard line where it is fielded by the other team. The returner (in an attempt to advance the ball) doubles back, losing yardage. He is eventually tackled for a loss at the 2 yard line. This is a 49-yard punt because there are 49 yards between the line of scrimmage and where the other team fielded it.
4. The line of scrimmage is the team's own 45 yard line. The punter kicks from the 30 yard line. The ball travels in the air to the other team's 6 yard line where bounces into the end zone (past the zero-yard line). By rule, this is a touchback and the other team get the ball on the 20 yard line. This is a 55-yard punt because there are 55 yards between the original line of scrimmage and the end zone.
Set aside the internal inconsistency in the distinction between (2) and (3). One could measure the length of punts from the point where the kicker kicks the ball. After all, on the 55-yard punt, the kicker actually kicked the ball 70 yards (64 of which were in the air). But, that's not how it is done... at least for punting.

Place kicking is another story. A team will kick a field goal if it believes that its kicker can kick the ball through the uprights on a place kick. If successful, a field goal is worth 3 points. By rule, drop kicking a field goal is not allowed. The ball must be kicked from the ground. The team that is attempting a field goal will snap the ball backwards approximately 7 yards to a holder who positions and holds the ball for the kicker who kicks the ball (hopefully through the uprights).

The uprights are positioned at the back edge of the endzone (which is 10 yards deep). Hence, a successful field goal must travel an extra 10 yards from the yard marker at which it is kicked.

For the official statistics, a field goal attempt's length is measured as the distance it must travel to be successful. Consider a couple of examples:
1. The line of scrimmage is the other team's 20 yard line. The holder holds the ball at the 27 yard line. This is a 37-yard field goal attempt because the ball must travel 37 yards in the air and go through the uprights to be successful.
2. The line of scrimmage is the other team's 20 yard line. For some strange reason, the holder holds the ball at the 32 yard line. This is a 42-yard field goal attempt because the ball must travel 42 yards in the air and go through the uprights to be successful.
3. The line of scrimmage is the other team's 35 yard line. The ball is snapped 7 yards back to the 42 yard line. This is a 52-yard field goal attempt.
A final note on field goal attempts. It doesn't matter if you make it by an inch or make it by 30 yards, the field goal you made is measured as the same length.

Now, you can see how place kickers (kickers who attempt field goals) and punters are assessed differently for the length of their kick. On his resume, a place kicker gets to add 17 yards (for a typical place-kicking formation) to the field position at which he can successfully make a field goal. On the other hand, a punter must subtract 15 yards from how far he can truly kick the ball. Seems unfair to punters.

Why the difference? I can understand that coaches want to know how far a particular punter will advance the ball when changing possession, but for a particular place kicker, they also want to know how far they have to advance the ball to have a good chance at a field goal.

From my perspective, both types of kicks ought to be measured from the line of scrimmage. Adding 17 to the field position seems like unnecessary addition when considering whether your kicker can make a particular field goal.

I'm guessing that field goals are -- in part -- measured this way for consistency across eras. In professional football, from 1932 to 1974, the uprights were positioned at the front edge of the end zone. Back then, there was no adding 10 for the length of the end zone because the ball didn't have to travel through an end zone. When the uprights were moved, the difficulty of making a kick from the 20-yard line changed.

Adding 10 to how it used to be done seems like a natural solution to making the measurement of kicks across eras consistent. Football historians may want to be able to compare the length of kicks in 1969 to length of kicks in 1984. For example, we might want to know if Jan Stenerud kicked a longer field goal in 1984 than his best in 1969.* As long as the measurement of the kicks is consistent, we can make this comparison.

Speculation aside, that still doesn't explain why we don't measure field goals from the line of scrimmage.

*His long in each year was actually the same: a 54-yard field goal. His longest was a 55-yarder in 1970.