A couple of weeks ago, Brian Burke of Advanced Football Analytics (formerly Advanced NFL Stats) wrote a great post on the value of a first down. From that post, we concluded that the marginal value of a first down is 9 yards, and we’ve previously determined that the marginal value of a touchdown is 20 yards. Therefore, we can create an Adjusted Yards per Carry statistic, which can be calculated as follows:
Adjusted Yards per Carry = (Rushing Yards + 20 * Rushing TDs + 9 * Rushing First Downs) / Rushes
If we use this metric to analyze the 2013 season, how would it look? Last year, the Eagles averaged 5.13 yards per carry and 8.29 Adjusted YPC, courtesy of the fact that the team led the NFL in rushing first downs. Philadelphia also ranked 1st in the NFL in both of those metrics and in overall rushing yards.
So what are the biggest differences we see when using Adjusted YPC compared to general YPC?
- The Dolphins ranked 17th in yards per carry, but just 25th in Adjusted Yards per Carry. One reason: Miami ranked last in rushing first downs with just 61. Lamar Miller may have averaged a respectable 4.0 yards per carry, but he gained just 27 first downs on 177 runs. For reference: Trent Richardson rushed for 27 first downs last year, too, on 188 carries.
- The Jets ranked 6th in rushing yards and 10th in yards per carry, but just 17th in AYPC. New York ranked 5th in rushes of over 25 yards, which helps the team’s YPC average, but long runs aren’t as valuable in Adjusted Yards per Carry.
- The Panthers ranked 16th in YPC but 11th in AYPC. That makes sense: Carolina loves to run in short-yardage situations, which tends to lower YPC averages. But if the team is successful, they pick up a 9-yard bonus, and Carolina ranked 2nd in rushing first downs in 2013.
- Denver ranked 20th in yards per carry and 14th in AYPC. The Broncos ranked 10th in touchdowns per carry and 11th in first downs per carry, so that was enough to offset the team’s mediocre yards per rush average.
- The biggest positive mover on the list was Detroit. The Lions ranked 22nd in yards per carry but 15th in AYPC. What gives? Detroit converted 19-of-24 times when running on 3rd- or 4th-and-1 or 2, the 6th-best rate in the league. The team was also 13th in touchdowns per carry. With Reggie Bush and Joique Bell, Detroit had a pretty effective running game in 2013 — well, let’s hold off on that statement for a moment — and the 22nd-place ranking in YPC doesn’t reflect that.
What if we bring in the Football Outsiders and Advanced Football Analytics rushing rankings? Take a look:
Football Outsiders was very down on the Jets running game relative to the team’s lofty YPC average; using Adjusted YPC helps in this case, although FO was even more negative on the team’s running game. The Panthers are another team where the use of Adjusted YPC helps bridge the gap between the team’s DVOA rank and YPC rank. Carolina ranked 16th in YPC, 11th in AYPC, and 4th in DVOA. In general, AYPC seems to “work”, if the goal is to make YPC look more like DVOA. One big exception is Detroit: Football Outsiders thought the Lions running game was even worse than its 27th-place YPC average. There’s a very good reason for that, but I’ll give you a minute to see if you can figure it out.
Using AYPC also helps converge the YPC rankings and the Advanced Football Analytics rankings. For example, Denver ranked 5th in AFA’s rankings and 20th in YPC, but 14th in Adjusted Yards per Carry. Carolina also ranked 4th in AFA’s rankings along with DVOA. In general, I find the evidence pretty persuasive — and this shouldn’t be a surprise — that if the intent is to mimic either DVOA or EPA, using Adjusted Yards per Carry is better than using Yards per Carry.
Of course, Detroit again is an outlier in the AFA metrics — the Lions ranked 24th in AFA’s rankings. So why do both FO and AFA place low grades on the Lions rushing attack, even though the team was better at gaining first downs and touchdowns than its YPC average would indicate? Because Detroit lost ten fumbles on rushing plays last year, the most in the league. In fact, the Giants, with 8, were the only other team to lose more than six fumbles in 2013.