Now, for the last three weeks I’ve been writing about some advanced football stats like expected points added or win probability.

Today, let’s focus on a stat that is relevant for most of the Packers fans as they get to see it all the time when praising RB Aaron Jones.

First, yards per carry over the course of a season seems to show the pure ability of a running back. But there’s a lot more to that:

The running back is not the most responsible figure for the success of running plays

Multiple studies have shown that offensive line play is a key factor for good running play. So a good offensive line can make room for every running back around; you don’t need to pay good money for a running back, just pay it for the O-Line! This, by the way, has the positive side effect that the (by the numbers) far more important passing play will profit as well.

The variation of the stat itself

Second, studies and data analysts have found that yards per carry is a highly variable stat. Aaron Jones might be the exception to prove the rule, because he posted 5.5 ypc in 2017 and 5.5 ypc in 2018 as well, but with most other running backs, there is no indication that X ypc in year Y show Z ypc in year Y+1.

Even worse, yards per carry is a stat that varies over the course of a season itself: Chase Stuart ( found in 2014 that Jamaal Charles averaged 5.8 ypc in odd-numbered games (1,3,5) and only 3.96 in the other ones.

This finding is not meaningless, because you cannot explain it “normally” by looking for the reason in an injury or something else why he might be better in the second half of the season than in the first half.

Oh, you can do the same for the 2018 season of Aaron Jones: He played 12 games in 2018, and in his 1st, 3rd, 5th and so on game he averaged 6.39 yards per carry – a number that is incredibly high – but in his 2nd, 4th, 6th game and so on he averaged only 4.21 yards per carry, which is not so impressive.

So what can you make of that?

Well, if another Packers fan brags about Aaron Jones averaging a pretty good 5.5 ypc in his two seasons in the NFL (2nd best in 2017, 4th best in 2018), you can tell him that Aaron Jones might be great and could and probably will impact the Packers’ offensive success in 2019, but not because he had two good seasons by yards per carry, but by his elusiveness, his overview to find holes in the defensive line and by his quickness off the line.

But how can I estimate a running back’s success in the future?

Now, that’s something NFL teams try to do all the time: Predicting the future. And you know what? They haven’t figured it out yet. Because then you wouldn’t need to play the game, if you could simulate it as well.

Football is a game that is so interesting because you CANNOT predict it. There are ways to try it, and there are valid conclusions drawn from data, but there is no way of telling a team will win that game because of stat A, B and C. It’s a game that is way harder to predict than basketball and infitely harder to predict than baseball.

Still, if you want to predict the success of a running back in the future, there are two stats that are not perfect, but better than yards per carry – so you should stick to that until something better comes along the way: Rushing attempts and total yards.

Now, really?

Yes. Many studies have found a pretty good correlation between rushing attempts and yards in year X and X+1.

And how do I know how good a running back is right know?

If you want to show how good a running back currently is, look at his expected points added, which rewards short-yardage situtations that lead to a new first down or a touchdown, because this is something I didn’t even mention until now: A running back that makes a trillion touchdowns from the 1-yard line still has a ypc of 1.0. In this case, the O-Line also makes a really big difference, but it’s still the most accurate stat that tells you the success of a running back.

Max Sachs is an international Packers fan from Germany. As a part of the Packers Germany, he tries to convince everyone around him to cheer for the greatest franchise on earth - or to start with, for American football in general. You can find him on Twitter @KaesekopfDE (the german translation for cheesehead).