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Stacking the Box Score: Third-and-long is no problem for the Kansas City Chiefs

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The numbers show Patrick Mahomes is better than most at converting on third or fourth-and-long.

NFL: Kansas City Chiefs at Chicago Bears Mike Dinovo-USA TODAY Sports

Welcome to this week’s Stacking the Box Score, where I’ll be quantifying what went down between the Kansas City Chiefs in their most recent game — in this case, a 26-3 win in primetime over the Chicago Bears.

As always, here’s a quick primer on some of the stats and data I’ll be using. If you already feel comfortable with these metrics, skip the link and keep reading!


Chiefs vs. Chicago Bears, December 22nd


Win probability

It was a pretty routine victory for the Chiefs on Sunday night. Patrick Mahomes’ quick dash to the end zone was the most impactful play of the game, adding 12% to the Chiefs’ chance of winning. The only other play that swung the game either way by 10% or more was the third-down conversion to Sammy Watkins on the Chiefs’ opening drive. After that, it was smooth sailing as the Chiefs slowly chipped away at the Bears chance of a comeback.

Converting that early third down was a big boost for the Chiefs on Sunday, but it likely wasn’t surprising to fans who have been following the team closely. In fact, if anything, that third-and-10 felt easy. It seems like the team has had no problem converting third downs from any distance — even really long ones.

So...is this backed up by the data?

I went back to all third or fourth-down conversions since the start of 2018, looking at how often all teams except the Chiefs converted at each distance away from the sticks. Then I isolated just the Chiefs, plotting that on the same graph.

The results were astonishing.

Kansas City has been a bit better than average at most reasonable third/fourth down distances (3-10 yards). This isn’t surprising, given their offense is better-than-average overall. However, the shocking numbers come when we get far away from the yard to gain, at 18 yards or greater.

Since Mahomes took over the helm, the Chiefs have been more likely to convert a third or fourth-and-18-plus than the rest of the league has been at just 5 yards deep. That’s... ridiculous. As I jokingly alluded to on Twitter, the team almost seems better off taking a sack or a penalty to start the drive to force them to be aggressive.

To contextualize this further, I looked at how many third/fourth-and-very long (18-plus) other NFL quarterbacks have completed since 2009 (as far back as our play-by-play data allows), relative to their total drop backs (in other words, after X many drop backs since 2009, this quarterback has completed Y many third/fourth-and-very long).

There are a lot of Mahomes charts that make me go, “wow.” This is definitely one of those charts. Despite having one-seventh of the dropbacks since 2009 as the league’s longer-tenured quarterbacks, Mahomes is fifth in total third/fourth-and-long conversions — and only two away from the throne (Joe Flacco).

To better show just how dominant Mahomes has been in these situations, I looked at Expected Points Added. Third-and-fourth-and very long typically has a very low expected points number — meaning, the offense is not very likely to score on that drive. So converting one of these plays goes a big way in boosting a quarterback’s EPA. How does Mahomes stack up from an EPA perspective?

This is the chart.

When we look at the Total EPA each quarterback has gained in these situations by the number of times they’ve been in these situations since 2009, Mahomes is quite simply the undisputed king. He has almost 10 more expected points added than the next highest quarterback. Now, it’s noteworthy that the majority of quarterbacks trend downwards as they face more of these desperate situations. However, that’s because those quarterbacks average negative EPA per drop back on these plays (failing to convert far more often than not).

Will this regression end up hitting Mahomes? My guess is not. Mahomes doesn’t handle these situations like the rest of the NFL does — he’s far more aggressive with the ball.

Throwing the ball deeper, while at larger risk of interception, leads to better outcomes on average. This becomes incredibly clear when we compare Mahomes’ success on third-and-very long to his peers, along with the above-air yard distributions. He isn’t afraid to sling the ball down field (no matter the weather), and this helps him convert at a historic rate.

So, next time you see the Chiefs with a third-and-18 or more, there’s no need to stress — though if you’ve been paying attention, you knew that already.