The San Francisco 49ers undoubtedly have the better defense in the Super Bowl 54 matchup, but the Kansas City Chiefs might have the most important defensive player. Sure, the 49ers have Richard Sherman and Nick Bosa, but the 49ers’ defense doesn’t revolve around either one of them like the Chiefs’ does with Tyrann Mathieu.

Late in the regular season, we highlighted how some of Kansas City’s additions in the secondary helped improve the defense from a liability in 2018 to unit that is more than capable of holding up in the Super Bowl. The addition of Mathieu was a big part of that improvement and his impact has only increased throughout the playoffs.

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As an offensive game planner, Kyle Shannahan has the habit of identifying the weak link on a defense and picking at it for an entire game. That weakness certainly won’t be Mathieu and his presence will make it harder to identify a weakness because Mathieu plays everywhere, which allows his teammates to move around and play to their strengths.

Since rookie safety Juan Thornhill was lost for the season with a torn ACL, the Chiefs needed to move around some defensive personnel. Kendall Fuller has played more safety while safeties Daniel Sorensen and Rashard Fenton have been on the field more often.

Defensive coordinator Steve Spagnuolo has put trust in Mathieu to line anywhere on the field. It helps that Mathieu might be the best at every position he’s been asked to play. Entering the Super Bowl, Mathieu could be considered Kansas City’s best safety, linebacker, and slot corner. A case could even be made for outside corner.

Part of what makes Mathieu so valuable is how instinctual he is on the field. This impact was evident early in the season for Kanas City. Below is a play from the Chiefs’ Week 3 game against the Baltimore Ravens backed up in their own red zone. Kansas City dropped back in zone. Mathieu first bumped the short crossing route over the middle of the field, but kept his eyes on Lamar Jackson. Mathieu then recognized the post route from Mark Andrews and jumped in front for a deflected pass and near interception.

Per Football Outsiders, the Chiefs went from 25th in DVOA against opposing tight ends in 2018 to fourth in 2019. Mathieu played a big part in that. But his biggest impact might be in how often and how well he’s been able to hang with opposing wide receivers. No safety was asked to cover wide receivers more often than Mathieu and among 44 safeties with at least 10 targets against wide receivers, Mathieu was seventh in yards allowed per target and had the second-most passes defensed.

Overall this season, Mathieu had 12 passes defensed, the second-highest total after the 17 he had in his All-Pro 2015 season. (Mathieu was also All-Pro in 2019.) Only Justin Simmons of the Denver Broncos and Marcus Williams of the New Orleans Saints had more passes defensed as safeties.

Mathieu’s awareness of where the ball is going and how he should play the receiver’s route in coverage has made him a danger to throw against. Even when he’s not the first to the ball, he has the ability to stay with the play like he did on a slot fade against Courtland Sutton in Week 15.

Mathieu’s ability to play all over the field also helps the Chiefs disguise what they’re going to do pre-snap. Take this play from Week 17 against the Los Angeles Chargers. The Chiefs came out in a two-high look with Mathieu and Armani Watts (23) deep. Rashard Fenton (27) was lined up across from the isolated wide receiver in a 3×1 set but just before the snap, he crept toward the line of scrimmage. At the snap, Fenton blitzed and Mathieu moved over to cover the outside as Watts replaced Mathieu as the safety to that side and Kendall Fuller (29) dropped back to replace Watts. Fenton was unblocked as a blitzer and forced Philip Rivers to get rid of the ball. Mathieu was able to break and undercut the out route to force an incompletion.

This also helps when the Chiefs are going to blitz. During the regular season, Mathieu and Sorensen were two of the most blitz-heavy safeties in the league. Sorensen blitzed on 9.6% of his pass snaps, while Mathieu blitzed on 7.5% of his, per Sports Info Solutions, and Mathieu just edged out Sorensen in pressure rate.

Safeties with at least 30 pass rushes, 2019 regular season

PlayerTeamPass RushesRush%Pressure%
Earl ThomasRavens387.0%31.6%
Chauncey Gardner-JohnsonSaints359.3%31.4%
Jamal AdamsJets7814.1%29.5%
Malcolm JenkinsEagles589.5%29.3%
Jordan WhiteheadBuccaneers467.9%28.3%
Eric ReidPanthers406.8%27.5%
Budda BakerCardinals457.1%24.4%
Tyrann MathieuChiefs457.5%24.4%
Daniel SorensenChiefs369.6%22.2%
Harrison SmithVikings345.9%20.6%
Shawn WilliamsBengals428.3%16.7%
Chuck ClarkRavens7717.8%15.6%
Kenny VaccaroTitans559.0%14.6%
Patrick ChungPatriots339.0%12.1%

Without Thornhill, the Chiefs haven’t blitzed quote as much but they have been playing with more defensive backs on the field, especially in obvious passing situations and late in games. In those packages, Kansas City has asked Mathieu to cover the short middle of the field and read and react to the offense. That’s worked out pretty well.

During the regular season, the Chiefs were first in defensive DVOA on passes to the short middle of the field after ranking 23rd on such throws in 2018. This is another place where Mathieu’s range, ability to diagnose the offense, and break on the ball becomes the key piece in how Kansas City can line up.

Here’s is a 3rd and 8 against the Chargers in Week 11. Mathieu initially lined up as the deep safety to the left side of the offense but at the snap, he rotated down to the short middle of the field as the safeties shifted behind him. Mathieu read a throw intended for Keenen Allen down the seam and he jumped in front for an interception without Phil Rivers having any idea he was in the area.

Mathieu has gotten more even more freedom in that area during the playoffs. The below play is a 3rd and 12 in the first half from the Divisional Round game against the Houston Texans. Mathieu started off as the slot defender and as Kenny Stills went vertical, Mathieu passed him off and broke in front of a DeAndre Hopkins crossing route.

Late in the game, the Chiefs came out in Dime and allowed Mathieu to sit in the middle and read the quarterback. Right at the snap, he read the quick back to Darren Fells and broke on the ball for what could have been a pick-6.

The 49ers offense has a number of ways it could attack an opposing defense. San Francisco has been able to pick on defenders all year. However the Chiefs decide to combat what the 49ers might do, Tyrann Mathieu is going to be the focal point. It’s not a stretch to say Kansas City wouldn’t be in the Super Bowl without him and it might be less of a stretch to say if they win, he’ll be a big reason why.