This analysis stemmed from a comment from NorthEast Cowboy about the relative weightings of 'pass' vs 'run' in total QBR. Specifically, does QBR overrate a good running QB?

As always with QBR, we do not completely understand how they rate players the way they do, but we can isolate out their pure 'pass' versus 'rush' scores and have a look at different QBs over time. For this analysis, when a QB has missed a season due to injury, I've simply provided an average of the season before and after that specific year to ensure we have a value in that year.

QBR only goes back to 2006, which limits my slightly, but lets start with two of the best pure passers of the modern era - Tom Brady and Drew Brees - huge caveat, we do not have data for the start of their careers, only from 2006 onwards. For every other QB we look at here, the data will be from the start of their careers.

Tom Brady, Drew Brees & Patrick Mahomes:

As you can see, they are very similar QBs. Neither is much of a running threat, and this hasn't changed much during their careers. Both are high quality 'passers' though. As you will see, to be consistently between 60 and 100 for the 'passing' component of QBR is elite. In fact, you could make an argument that Brees is the better pure passer. I've added Patrick Mahomes to this analysis, just because it seems like the best comparison. From a passing point of view, he already looks like he may top both Brady and Brees. He also has the additional running component, that seems to be trending upwards (as you will see below, this is quite unusual. Quite the unicorn!!

Some QBs just don't have enough data for an effective comparison, but if you were going to add a young QB to this list, it would be Herbert. In terms of pure passing, we would be nearly up there with Mahomes.

Aarron Rodgers, Matthew Stafford & Matt Ryan

Next up - three QBs who have all been around a long time, all have at least been to a superbowl and would generally be regarded as high end NFL QBs. Let's be honest, Rodgers is often placed in the same sphere as the likes of Brees and Brady. If we firstly look at the 'passing' element. Ryan is the most consistent by far. He is a notch below Brady and Brees, but across his career, he has been consistently good. On this data alone, Rodgers is nowhere near as consistently good as Ryan - in fact he rarely beats Ryan on pure passing alone. He is capable of very good seasons though. Stafford has only been OK from a passing point of view, apart from one season when he won it all. In terms of running QBs, neither Ryan or Stafford are thought of in this way and the stats back this up. Rodgers is thought of more of a scrambler, and this is the first bit of evidence that maybe the 'running' component of QB play declines with age. You can definitely see a drop off over the past few seasons.

Russell Wilson & Cam Newton

The next analysis looks at two QBs with sufficient data, who would be considered running QBs. Wilson more of an elusive type of runner versus Cam who was more of a power runner. If we look at the 'passing' element first, both are somewhere below the 5 QBs we have already looked at. Wilson is clearly the better of the two, and is relatively consistent, albeit in the 40-60 range. Pretty middling QB play from a QBR perspective. Cam is pretty bad, which is what you would expect. If we look at the 'running' component of QBR, then both are consistently higher than the 5 QBs we have looked at so far. Cam is the more consistent runner (just about), but again, you can see a drop off as the QB starts to age.

If you wanted to pick out current 'running' QBs with limited stats - the closest comparison to Newton would be Hurts and Jackson, the closest comparison to Wilson would be Murray and perhaps Jones. Personally, I wouldn't touch Jackson with a barge pole. Both his passing and running stats are trending downwards. As a runner, he matched Cam very closely, although he is definitely a better passer. However, he is still middling at best and trending downwards. Hurts is a tougher read with only 2 full seasons behind him. Both his running and passing are trending upwards. At present, he looks a little like Russell Wilson Year 3-4. If I had to guess, I'm not sure his type of running is sustainable, and as yet, his passing grades are only OK. Murray has the highest passing grade out of all the QBs in this section, although he just had a bad season. His rushing stats are more like Wilson's - a little up and down. Jones also looks a little like Wilson in terms of career trajectory.

Overall, i think the Newton style of running is more likely to decline faster than the Wilson style of running, but both tend to decline with time. Outside of Murray, none of these QBs have shown the 'passing' ability associated with the top end QBs. Doesn't mean some of them won't, but I'm not sure I'd risk a 2nd contract for any of them.

Dak Prescott, Jared Goff & Carson Wentz

Seems appropriate to compare the 3 QBs from the same class. From a 'passing' point of view, Dak is the best QB. He started well, then dropped a bit, then was on a fairly steady trajectory upwards until this season. Is it a blip? Or can we expect consistent decline? Who knows. His pattern is relatively similar to Matt Ryan i.e. in terms of pure passing, Dak is a pretty good QB. Until this season, Goff has been a pretty consistent middling NFL QB. This season has seen him trending upwards. The Lions are also on the up, so maybe this will continue. Wentz has been trending downwards for a number of years, albeit his stats are quite volatile. In terms of running, Goff is as bad a running QB as you will find. Wentz has been consistently OK. Dak started off as a high level runner, but has seriously declined over the years - further evidence that the 'running' component of QB play is the most likely to decline over time.

Overall, based solely on the passing component of QBR, the elite QBs tend to hover around 80 (and there aren't many of them). If you can consistently score over 60, then you are probably a top 10 QB in this league. Clearly Dak falls right in that range. From a passing point of view, he does seem to be capable of more than a lot of his contempories. It does seem to be the case that the running component of QB play is likely to decline with age, and that the more physical you are, the faster that dropoff might be,