Chiefs-49ers: Super Bowl analytics preview

You’re likely well aware of the Kansas City Chiefs’ strengths and weaknesses. They pass the ball very well — and very often. They don’t run the ball very well — or very often. They defend against the pass better than most teams. And recently, their run defense has been passable — if not good.

You’ve also likely heard a lot about their upcoming Super Bowl opponent: the San Francisco 49ers.

A lot of that discussion has centered around the 49ers demolishing the Green Bay Packers in the NFC championship game — specifically the dominant performance of Raheem Mostert. The 49ers running back trucked through the Packers to the tune of over 200 total yards — and over seven yards a carry.

And this isn’t a case of box score deception. Mostert absolutely carried the team to victory, averaging 0.5 Expected Points Added (EPA) per carry — a number higher than Patrick Mahomes passing EPA per attempt during his dismantling of the Tennessee Titans in the AFC championship.

Wow.

However, that performance has led to some extreme recency bias among NFL analysts, media and fans. Much of the discourse about the upcoming matchup has surrounded around Kansas City’s presumed inability to stop the 49ers’ dynamic running game.

But is the run game really what has propelled San Francisco to victory all season — or even recently? Or was the NFC championship just an outlier that is swaying our perception of the reality?

49ers Offense

First, let’s look at which facet of the offense has contributed more to the teams’ scoring chances - by using total Expected Points Added (EPA) per game.

This may be surprising to those who only watched the 49ers against Green Bay. But this season, the 49ers have actually added far more to their scoring chances through the air than on the ground. In fact, in only three games was the running game more effective than the passing game.

So we know that the San Francisco offense is more effective through the air than the ground — but that’s the case for most teams. How do the two units stack up when we look at them relative to the rest of the league?

To answer this, I started with San Francisco’s total EPA gained by the pass and run — and then subtracted this season’s average EPA in both categories across the league. This will tell us how each type of play helped the 49ers relative to the league average.

To better visualize this, I then plotted the difference between the two types. A positive value means that relative to league average, San Francisco’s passing attack was more valuable in a given week — while a negative number means the opposite.

This paints a far more balanced picture of the team. For most teams, passing is inherently more effective than rushing. Yet San Francisco has depended on rushing almost as frequently as they have on passing.

While that means the Chiefs would be wise to study up on Mostert and Matt Breida, they certainly can’t ignore Jimmy Garoppolo. In fact, Garoppolo averaged 0.25 EPA per dropback this season — good for seventh in the league. Meanwhile, the team’s EPA per carry was good for ninth in the league. This relative balance — but with a slight edge to the passing attack — matches with what we see here.

Where have the 49ers found success in the passing game?

Well, here is where Jimmy Garoppolo has been throwing his passes this season compared to the rest of the league’s quarterbacks.

The scale on the right tell you how to read the chart. The areas of red show a higher density of passing targets than average. The blue areas show areas where the targets are below the league average.

But this chart looks familiar, doesn’t it? Uh oh.

This chart — which shows where the Chiefs have allowed passes to be more easily completed compared to the rest of the league — demonstrates two vulnerabilities of the Chiefs passing defense: screen passes and throws to the short middle of the field. Garoppolo and the 49ers happen to target those areas of the field more often than the rest of the league.

49ers Defense

What about the flip side of the ball?

This season, the 49ers ranked second in passing defense, limiting opposing quarterbacks to minus 0.13 EPA per drop back. The team’s run defense was good, but ranked only 11th-best in EPA per carry. Interestingly, these rankings exactly match that of Football Outsiders’ DVOA metric, which adjusts for opponents.

What does this mean for the Chiefs and Patrick Mahomes?

Well, a large part of the 49ers’ prowess against the pass is thanks to amazing play from cornerback Richard Sherman. This year, Pro Football Focus said that among cornerbacks, he turned in the highest-graded season of the past decade — and he has been pivotal in shutting down opposing passing attacks.

That said, he may not pose as big a problem for the Chiefs as you might think.

Unlike other top defensive backs like Stephen Gilmore of the New England Patriots, Sherman does not shadow opposing teams’ top wide receivers — like Tyreek Hill this Sunday. Instead, the data from Next Gen Stats in this chart shows that he sticks to one side of the field.

As I wrote a few weeks back, Hill is among the leagues’ most versatile receivers; he can (and does) attack any part of the field. The same can be said for Chiefs tight end Travis Kelce. This means that while the 49ers best coverage option is limited to one side of the field, head coach Andy Reid can move his offensive weapons to wherever they can get an easier matchup.

Relative to the rest of the league, the 49ers do have a strong running game — but like most teams, their passing attack has still been the main driver of their offense. We’ve also found that Garroppolo may tend to target areas of the field where the Chiefs pass defense is weakest — which thankfully aren’t the deepest parts of the field. The 49ers’ passing defense will be the second-best Mahomes has faced all year, but is limited in a way that Reid might be able to attack.

And at the end of the day, this is an offensive league. When it’s strength versus strength, offense usually wins.