Tracking the 2017 RB class: Marlon Mack

This article is an installment of a series in which I use my Observational Rushing Numbers (ORNs) to shed light on just how good the 2017 rookie running backs were at carrying the ball. You can find each previous article about these numbers on the series’s hub.

To this point, none of my articles have claimed anything too controversial. Christian McCaffrey and Joe Mixon played behind terrible offensive lines, didn’t have great showings themselves, and had poor yards per carry marks as a result. Leonard Fournette was pretty good, needs to clean up his vision, might’ve gotten lucky with big runs, and probably saw his ORNs suffer from fatigue. To some extent, this is probably good; it’d be hard for my stats to hold credibility if they kept contradicting commonly-held beliefs among the NFL world. Of course, I also wanted some spice when I set out with this series.

I sure got that with Marlon Mack. The fundamental purpose for my numbers is to highlight how good a back and blocking unit are at contributing to yards per carry (and thus more generally, rushing productivity). So, when I say that Mack grades out in the ORN rookie elite, I’m saying that of all rookie running backs, he contributed to the running game nearly the best of anyone. If you want that to mean that he was one of the class’s best backs last season, go ahead. You can also point to a small sample size, and some regression to the mean is certainly in store, but there’s little indication within the data that he actually got lucky.

Now, I will say that Marlon Mack’s 2017 Observational Rushing Numbers are in the top tier of rookie backs. No matter how you slice it, his 2017 was better than a ton of big names, and there isn’t great reason to see that changing. Let’s look at the how and why.

(I’ve taken these tracking stats from Weeks 1-14 for each rookie running back with at least 75 carries. If you’re wondering what any of the stats mean in a fuller sense, check the series glossary.)


At a glance

Four Big Stats and Class Radar



Mack finished third of all rookie backs in RB Composite (a single-number, overall stat that measures a back’s ability to contribute to Y/C) despite finishing below-average in two of three sub-stats. Logically, then, his HGY/C (how well a back generates yardage after they’ve hit a hole) must have been incredible. Incredible, it was:


There’s a lot more to discuss when it comes to Mack’s running game, but his explosiveness is the defining trait. When his other skills faltered, he was still one of the class’s most productive backs because of that creative ability.


Success Rate

While this article’s tone has been quite positive to this point, I should take a step back and say that there’s still plenty that Marlon Mack could be better at. His Success Rate was third-worst in the class, meaning he wasted the third-most opportunities that his offensive line provided for him. Behind such a travesty of an offensive line (which we’ll touch on later), that’s especially troublesome.

From the radar, we can confirm from his Hit Rate (how well he hits holes that he has identified) that he wasn’t suffering from physical limitations; rather, the problem was how often he didn’t run to a hole that the OL opened for him (what Identification Rate — ID Rate — measures). Directly plotting Hit Rate against ID Rate further illustrates his issue:


Unlike Christian McCaffrey, who posted the class’s worst ID Rate, I don’t see Mack’s ID Rate rising too much in the future — if he sticks to his current running style. Qualitatively and quantitatively, that style is quite similar to LeSean McCoy’s, which sacrifices consistency (via hitting fewer holes) for explosiveness when hitting those holes. They make that trade-off by bouncing runs when there are surer paths straight ahead and by sometimes reversing the field when there isn’t much room ahead. For most backs, those are highly unwise decisions; however, for leaner, athletically superior backs who can superbly dodge tacklers (Mack and McCoy are very much on that list), those decisions are smart in the aggregate: HGY/C’s weight doubles Success Rate’s in the Supercomposite. Simply put, that means if you trade an equal amount of your hole-hitting ability for creativity, you benefit (via increased yards per carry).

Mack is an imperfect back with definite strengths (athleticism, shiftiness) and weaknesses (power), and his running style amplifies those highs and lows. As long as he keeps running like this, he’ll have a low ID Rate, paired with other similarly-poor consistency numbers. But, evidenced by his final RB Composite standing, he’s made the correct calculus.


Hit Generated Yards

The most uncertain issue I’ve worked with while evaluating Mack’s performance comes in determining how much of a role his small sample size played in his astronomical HGY/C mark. On one hand, you can look at his H 10+ Rate (how often he generated at least 10 yards after hitting a hole on standard runs) and see that his 8.13 HGY per carry weren’t independently lucky:

hgy plot

If anything, we’d expect a back with so many runs into the second level to have generated even more. 

Of course, the other thing that graph tells you is how comically far Mack’s overall creative performance, all included, was from everyone else’s. He’s an awesome generator, but he’s not playing on a level that far above that field — a sample that includes every 2017 rookie back and LeSean McCoy in 2016, among others. Obviously, there’s regression to the mean in store, and there should be plenty of it. The question is, instead, comes in determining just how much regression that will be.

This discussion leads me to reflect on how I evaluated him after he was drafted, for a reference point. From my rookie profile in April 2017:

Marlon Mack might be this rookie class’s most thrilling back to watch. He is certainly not the best, but can catch everyone off-guard with huge plays unlike any other back. In 2016 alone, he scored six touchdowns from at least 43 yards out. He takes off with maybe the best burst in the class, and pulls away from any defender he has already passed.

Breakaway acceleration and speed make up much of the open-field creativity equation. After observing that explosiveness both in college and the NFL, I can confidently say that he’s mastered at least one part of space play.

The trick now comes in identifying how well he does the other important things — how well he makes it to breakaway opportunities and how well he dodges tacklers when there’s no clear takeoff point.

It’s tough to evaluate that first point: I don’t have an observational stat that has anything to do with breakaways. Even if I did, it’d be so infrequently and subjectively used that I wouldn’t be able to rely on it for serious analysis. My best effort to assess how well he gets to intermediate areas is to look at his hit generated yard rates. For reference, here are GY rates by rookie, with Mack inside the black box:


As previously shown and mentioned, his H 10+ Rate is off the charts, but taking one step back, his 45% H <4 Rate is also very strong (in a sense that its low-ness is a good thing); it means that on 55% of his runs, he generated at least four more yards than the replacement back (only three of 14 rookie backs did better). In other words, he generated yardage in the intermediate areas almost as well as anyone.

Fortunately, it’s a lot easier to judge how well a back break tackles. Looking at his Broken Tackles per Hit rate (self-explanatory) in the class radar, we can see that Mack certainly shook tacklers in that small sample size with great success. He broke more tackles when given an opportunity than any other rookie, as well as veterans like Todd Gurley, Melvin Gordon, and Derrick Henry. I am hesitant to conclude that he’s one of the league’s best with such a small sample size, but it’d take quite a long run of unsuccessful carries to make him a below-average tackle-breaker.

So let’s wrap things back up after looking at Mack’s scale-breaking HGY/C in depth. Three big things go into how well a player creates in space: how well they get past potential tacklers, how well they make it to breakaway points when given the opportunity, and how well they breakaway from pursuing defenders when they’ve reached that spot. I’d say it’s safe to call him “pretty good” in the first, “good-to-great” in the second, and “awesome” in the third. Those are consistent pluses, and consistently strong pluses at that. Thus, my best guess is that once Mack falls back down to Earth with a greater sample size, he’ll still be among the league’s (or, at least, the class’s) best when it comes to generating yardage in space.


Stuff Generated Yards

If Mack’s HGY/C is going to fall back and his Success Rate won’t get any better, then he’ll have to put up a better effort in limited space (what SGY/C measures) in order to make up for it. In his rookie campaign, Mack generated just 0.67 yards on stuffs — runs in which the offensive line fails to open a running lane. However, looking at his S 3+ Rate (how often he generated at least three yards on stuffs on standard runs) in the same way we viewed his H 10+ Rate tells us that we can be optimistic about Mack’s SGY/C rising in the future:


As can be seen by how well the points fit the trend line, we’d expect someone who generated a chunk of yards as often as Mack did to have a much higher SGY average. In fact, looking back at his class radar, Mack had one of the class’s best S 3+ Rates. Because generated yard rates are probably more likely to hold up in the future (that’s my hunch, at least), I’m confident that Mack will be able to contribute a lot more in tight confines in 2018 — even if he doesn’t actually get any better. Of course, he could also gain skill and thus push his SGY/C mark even higher.

The point is, he could make up for falling quite a bit in the open-field by rising quite a bit in limited space — and the underlying numbers indicate that that should happen to some extent even if he doesn’t gain any skill.


Run blocking

Three Big Stats

OL nums

Yeahhhhhhh. While they were passable at creating opportunities for Mack (measured by Hole Rate), the Colts blocking unit offered him a single rushing yard as a baseline (measured by OL-GY/C); in other words, an entirely replacement-level back would average 1.0 yards per carry running behind this line. Let that sink in. This is how much worse the Colts blocking was at generating yardage than the rest of the units I’ve sampled:

Alllll the way over to the right are the Colts. Multiple teams generated more than three times as many yards.

The next lowest mark for a blocking unit was 1.3 yards per carry, and the next lowest mark was 1.6. Similar to Mack’s HGY/C, the Colts’ OL-GY/C had such a strong magnitude that it entirely canceled out Hole Rate in the OL Composite… in a bad way this time.

Because of how it’s derived — OL-GY are counted until the first spot a replacement-level back would be tackled, then the back gains credit for all further yardage — a poor OL-GY/C mark tells me one (or two) of two things about an offensive line: (1) It couldn’t get any push. (2) The weakest links are especially weak. Looking a bit further into the stats, the latter point is clearly the case. By looking at the proportion of carries in which the offensive line generated some amount of yards per carry, we can see which allowed penetration more than others (and plenty more), beyond a single average. Putting those percentages into a running total on a graph, we can see the net effect even better:

The Colts are represented by the blue line with white dots. Indy gave Mack nothing (less than or equal to zero OL-GY) on almost 50% of its carries. The league average, thus far, is 32%.

That graph is generally an absolute mess to sort through, if you’re looking for information on an individual team… unless you’re looking at that blue line that’s above the rest, or the green one that’s below the rest (a story for another day). As we can see, Mack got confronted at or behind the line of scrimmage far more than any other back.

Generally, negative OL-GY on a run means a single defensive lineman or linebacker got penetration into the backfield; while it’s on the whole of the unit to open a hole for the back, one guy’s screw-up can lead to negative OL-GY. So, we can clearly see that there was at least (and probably, more than) one Colt offensive lineman who didn’t belong on the field.

Someone who’s more involved with the Colts than me probably has a better idea of whom those players are. But, with a simple glance at their 2017 snap counts, I’d guess that it wasn’t a single individual: After three offensive linemen (one tackle, one guard, and one guard/center) who played virtually every snap, nine guys logged between five and 39 percent of the team’s offensive snaps. The Colts cycled guys around the depth chart over and over again. Unfortunately, a lack of stability is a recipe for failure up front, and that is precisely what Indy got in 2017. It’s a bit of a miracle that such turnover didn’t lead to a worse Hole Rate too.

As for how 2018 goes, I’m conflicted. There is plenty of good news: It’ll be hard for Indy to jumble the offensive line as much as they did last year. They return each of 2017’s three mainstays, as well as five of the nine plug-ins. Matt Slauson heads into the unit with 108 career snaps under his belt too. Most importantly, the Colts drafted two promising guards in Quenton Nelson, a human monster, and Braden Smith, a person I played high school football against (and also a high-second round pick).

On the other hand, all three of those additions project as guards, so only two can play at once. Even then, guard was the one place that was stable in 2017. They’ll be relying on continuity to fix up the rest of the offensive line.

Still, on paper, I can see this group working out if it can get lucky with injuries. I like what they have to work with at guard, between Slauson, the two rookies, and Jack Mewhort — a starter for the first five games before getting hurt, currently slotted to start at right guard. Ryan Kelly has pedigree at center, and perhaps could’ve helped the Colts more if he were healthy for the entire season. Left tackle Anthony Costanzo is a steady hand at this point. You’d figure Indy can find someone to fill in at right tackle with the rest of their pieces.

The problem is that if one or two of those guys get hurt, the Colts will probably get thrown right back into the lava. It feels like a cliche to say that this unit will rely on staying healthy, given that the statement applies to every offensive line, but the drop-off looks particularly steep for Indy. (On a tangential note, this really doesn’t sound like a situation I want to throw Andrew Luck’s shoulder into.)

A silver lining? It’s going to be hard for this unit to get worse at run blocking in 2018.



It certainly wasn’t boring to look at Marlon Mack’s rushing profile. His creative stats were in a world of their own. His hole-hitting numbers, meanwhile, were among the class’s worst. His offensive line stood out from the rest — for all the wrong reasons. A lot of this was probably impacted by a small sample size. But, that doesn’t mean we should simply wave it off — we should take a closer look.

Upon further review, from all that can be seen both on the field and statistically, Marlon Mack was the best open-field creator of the 2017 rookie running back class last season. Because that’s a huge part of how well a back contributes to rushing efficiency, Mack was, in turn, one of the class’s best running backs, period. Although he’ll come back to Earth to some degree this season, it’s hard to argue that he won’t be pretty dang good. All that can really hold him back are a pair of fairly intriguing rookie backs… as well as the worst offensive line of the 20 units that I’ve tracked. Oh, shoot.

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