Stacking the Box Score: Two unsung heroes of the Chiefs’ Super Bowl run

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.

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. Tennessee Titans, January 19th

The Kansas City Chiefs are going to the Super Bowl. I repeat: The Kansas City Chiefs are going to the Super Bowl.

There’s a lot of stats that came out of this 35-24 victory that gave Kansas City the AFC championship.

Patrick Mahomes has now averaged a higher Expected Points Added (EPA) per dropback than any quarterback over the past 11 postseasons. As the chart shows, some quarterbacks have had a higher Completion Percentage Over Expectation (CPOE) in the playoffs, but Mahomes stands alone in the statistic that is based on putting points on the scoreboard.

Here’s another: the Chiefs defense backed up Frank Clark’s words, holding Titans running back Derrick Henry to minus 0.08 EPA per rush — and just 3.6 yards per attempt.

But those stats don’t capture just how special this game was. You already know how good Mahomes is — and how the defense showed up big.

So I wanted to take a different angle. Throughout the season, have there been Chiefs players who have made a big impact — without necessarily splashing on the scoreboard?

So I went to a new data source: SportsRadar, which allows us to see who is on the field for each play. By restricting our statistical calculations to only when specific players are on the field, we can get some answers to that question.

For the Chiefs, one player sticks out head and shoulders above the rest. Any guesses?

That’s right: Sammy Watkins.

The Chiefs passing offense is nearly twice as efficient when Watkins is on the field, averaging a whopping 0.30 EPA/play when he’s there (about 500 regular-season snaps), and just 0.16 when he isn’t (approximately 160 regular-season snaps).

No other player has such a drastic split. Except for Patrick Mahomes, no other player has a higher efficiency. This has paid huge dividends this postseason. As this chart shows, among all pass catchers in the postseason, Watkins has the highest EPA per target.

Is there an equivalent to Watkins on the defensive side?

I give you... defensive tackle Mike Pennel.

When Pennel was on the field during the regular season, the Chiefs limited opposing defenses to minus 0.09 EPA per rushing attempt. But without him, the Chiefs defense gave up 0.05 EPA per rush. That’s the difference between a 10th-ranked run defense and a 30th-ranked run defense!

In the playoffs, Pennell’s presence has also worked in the Chiefs’ favor. Much has been made of the fact that Pennel was inactive in the first game against the Titans, in which Henry rushed for 8.2 yards per attempt. But on Sunday, they held Henry to just 3.6 Y/A and minus 0.08 EPA per rush. In the two previous postseason games, he’d been averaging 5.6 Y/A and 0.03 EPA per rush.

And one last unsung hero: the Chiefs offensive line.

On Sunday, Next Gen Stats data reveals that Mahomes had an average time to throw (the time from the snap of the ball until the quarterback releases it) of 3.39 seconds. That’s the second-longest in any of this year’s postseason games — behind the Divisional round game for Russell Wilson, who is well-known to hold the ball for a long time. That figure is well-above Mahomes’ regular-season average of 2.82 seconds.

With that much time to throw, the Chiefs offense is clearly unstoppable — and for that, the offensive line deserves credit.