Sunday, October 3, 2010

The Long Field Goal

Your team has just stalled their drive at the 35 yard line, and your kicker has a pretty good leg. Send on the field goal unit, right? We're seeing teams sometimes elect to punt or go for it... which is right?

Using average points per drive numbers, we see that pinning the opponent deep means they can expect to score about 0.7 points on the ensuing drive. Missing the field goal pushes this number up around 3.0 for a net loss of 2.3. Even if you make the field goal, your opponent will average 1.6 points on the next drive, netting 1.4 points. Kickers convert on long field goals about 50 percent of the time, meaning the likely outcome is a loss of 0.8 points per attempt. In other words, the long attempt is about as good as pinning the opponent deep, especially when factoring in that your punter might put the ball in the endzone.

But, what about going for it? Getting the first down ups the average score to 3.6, for a net of 2.0 after factoring in the ensuing drive from the other team. Failing to convert yields the same 3.0 to the other team as missing the field goal does, so the conversion would have to succeed about 60 percent of the time to break even.

Turns out that all the options are pretty even, and this is really an area where a coach can make their money by having a good feel for the right play to call.

Friday, October 1, 2010

Buying 4 points

Teams try all manner of improving the defense, but it's a complex machine with many moving parts. What if there were an easier way to keep points off the board? A ball-control offense does the trick, but that tends to score fewer points.

Turns out there's a very simple, side-effect free, but hypothetical way to do this. The Cowboys got it half right last year. I've charted every drive from the first 20 games of this year and quantified a fairly obvious truth: the farther back a team starts its drive, the less likely it is to score. When a team starts inside its own 10, it averages about 0.67 points per drive. When it starts past its own 40, that number rockets up to 3.0. Here are the ranges and average points scored:

1-10: 0.67
11-20: 0.70
20 yard line: 1.00
21-30: 1.60
31-40: 1.75
40+: 3.0

The average starting field position for a team accepting a kickoff is its own 26. 2 yard line.
Suppose we could find a player whose only job it was to kick a ball through the endzone, time after time. The average team in 2009 kicked off just about 5 times a game. According to the chart above, we'd shed about 3 points allowed per game!

Charting offensive yards vs points scored yields a highly correlated best-fit line showing that a team scores 1 point for about every 9.1 yards over 143 they gain in a game. So, a team gaining 250 points can expect to score about 12 points in a game, 360 yards yields 24 points, and 500 yards comes out to around 40. By this metric, a savings of 6.2 yards, 5 times a game, saves about 4.5 points. Even better! (but we'll use the first method)

Want a bonus? Since our kickoff duties have been offloaded to Mr Cannonleg, our field goal kicker can be optimized for accuracy. Teams attempted an average of 1.8 field goals a game, and converted at an 81 percent rate. The best kickers in the league hit about 10 percent more often than that, resulting in an extra 0.54 points per game. Replacing an inaccurate kicker? The bottom of the league is another 10 percent below the average, so the net effect would reach 1 point per game.

And sprinkles on top (though now we're being a bit silly)? The concept extends to punts too. Teams punt 4.8 times per game, of these 1.6 are downed inside the 20 and 0.4 result in touchbacks. If your punter can keep those touchbacks out of the endzone, that's another 0.12 points. Drives starting after punts yield 1.36 points. Mat McBriar was able to punt past the 20 57% of the time, which was 15% better than the league average. If the average team could improve by that much, they could expect to give up 0.72 points less per game. In short, improved punting could improve your team's defense by over 0.8 points per game. Can your cannon-legged kicker always get a touchback? The benefit jumps to 1.73 points per game! Even if your average punter is replaced by McBriar, about half a point is saved.

Points saved per game over average for
always kicking a touchback: 3.0
having an accurate field goal kicker: 0.5
* always punting a touchback: 1.7
* always punting inside the 20: 2.7
being best at punting inside the 20: 0.5
*- these are kinda ridiculous ...

Now for the hypothetical part: there has never been a kicker who could kick that far, that often. I suspect there are some soccer players out there who could achieve results close to these, especially in warm weather/indoor stadiums. They could probably be signed for minimum contracts and the benefit is probably bigger than keeping an extra special teams or backup player on the active roster. How much bigger? There's a very strong correlation: for every 2 point differential a team averages, it gains a win. 3 points, 1.5 wins per season. Tell me that's not worth it.