If I had to put together a list of the most-hyped story lines ahead of Super Bowl LIV, the Chiefs’ late-season defensive renaissance might not crack the top 10. This game features two fun and creative offenses under Andy Reid and Kyle Shanahan; pits Patrick Mahomes against Richard Sherman, Nick Bosa, and the 49ers’ stifling defensive unit; and highlights two elite tight ends in George Kittle and Travis Kelce. It’s not a surprise that Kansas City’s defense has flown under the radar.

Expectations are predictably pretty low for how that group will fare against the balanced and highly efficient San Francisco offense on Sunday. Kansas City’s defense has struggled to shake its well-earned bad reputation; it was a liability for most of the 2018 season―a reality that was hammered home in the team’s 37-31 loss to the Patriots in last year’s AFC championship game―and after getting a comprehensive reboot under new coordinator Steve Spagnuolo, that group was still a massive vulnerability through most of the season’s first 10 weeks.

But the Chiefs defense is actually riding a quiet hot streak, and could have an outsize impact on Sunday’s game against the 49ers. With some new-found multiplicity under Spagnuolo and some much-needed swagger spurred by All-Pro safety Tyrann Mathieu, Kansas City’s defensive unit has transformed from a liability to a strength in the past two months―and will have a chance on Sunday to prove that its recent turnaround is no fluke.

The Chiefs were never going to fix a defense that finished 26th in Football Outsiders’ DVOA in 2018 overnight, but the team got the ball rolling by making a handful of key moves in the offseason. Kansas City fired defensive coordinator Bob Sutton, hired Spagnuolo, traded pass rusher Dee Ford, acquired Seahawks defensive end Frank Clark, and signed Matheiu, cornerback Bashaud Breeland, and linebacker Damien Wilson in free agency. Those changes created marginal improvements but weren’t enough to instantly revamp the team’s defense, especially with Spagnuolo installing a new scheme. Kansas City experienced some growing pains to start the year; through 10 weeks the defense ranked 19th in points allowed (23.9 per game), 17th in defensive DVOA, tied for 14th in takeaways, and tied for 23rd in touchdowns allowed (29). It seemed that once again Kansas City’s high-octane offense under Reid and Mahomes would have to carry the team to wins week in and week out.

But in the team’s 24-17 win over the Chargers in Week 11―when they created a season-best four takeaways―something began to click for the Chiefs’ much-maligned defense. Kansas City began to coalesce into a more disciplined, ball-hawking unit―communicating more effectively while playing with some much needed brashness. In the team’s final six regular-season games, Kansas City surrendered just 11.5 points per game―fewest in the league―allowing NFL lows of just seven touchdowns and an opposing passer rating of 63.5 in that stretch, while collecting 10 picks, tied for the league high. They didn’t exactly face a murderers’ row of quarterbacks in Derek Carr, Drew Lock, Tom Brady, Mitchell Trubisky, and Philip Rivers during that stretch, but the Chiefs’ numbers were impressive nonetheless.

Thanks to that late-season surge, Kansas City finished the year 14th in Football Outsiders’ defensive DVOA—a 12-spot improvement over 2018—and, crucially, that group has continued to play well in its two postseason games. Instead of being the potential Achilles’ heel some thought it might be for Kansas City, the defense has performed well on the team’s road to Miami. The 31 points Kansas City surrendered to the Texans in the divisional round is misleading, skewed by the touchdown that Houston scored on a blocked punt and by the short field its offense was gifted when Tyreek Hill muffed a punt at the Kansas City 6-yard line (the Texans scored one play later). Take those two flukey touchdowns away and the other 17 points Kansas City surrendered gets you closer to the team’s actual performance in that game. Kansas City held the Deshaun Watson–led aerial attack to 6.1 yards per pass attempt while sacking him four times and limiting Houston to 94 yards on the ground.

The Chiefs defense played well in the win over the Titans in the championship round too. Kansas City’s typically porous run defense came up big when the team needed it most, holding the previously unstoppable Derrick Henry to just 69 yards and a touchdown on 19 totes, limiting big plays and stifling Tennessee on early-down runs. Henry averaged just 3.7 yards per carry on his 18 first- and second-down runs in that game after averaging 5.1 yards per carry on those plays the prior two outings. That lack of success on first and second down consistently put the Titans offense behind schedule and forced the team into much tougher third-and-long situations. From there, the Chiefs pass defense took over, holding Tennessee to 6.0 yards per pass attempt and sacking Ryan Tannehill three times in the 35-24 win.

Mathieu has been the key for the team’s coverage unit since its turnaround in Week 10. The Honey Badger has returned to his roots as a positionless playmaker for Kansas City, lining up at safety, in the box, at slot corner, and just about everywhere in between. According to NFL Next Gen Stats, Mathieu has given up the fewest yards per target in coverage among all defensive backs this season (just 5.3 yards per target), and his ability to move around the defense and take away opponents’ top pass catchers could pay dividends against the 49ers on Sunday, particularly in his ability to match up with all-world tight end George Kittle. Kittle is a big threat, but Mathieu’s flexibility has played a big part in the team’s fourth-place rank in DVOA against opposing tight ends this year (they were 25th in that metric last season).

Multiplicity has been the name of the game for the defense’s entire back seven in its late-season run. Following the season-ending ACL injury to rookie safety Juan Thornhill, Kansas City has deployed slot corner Kendall Fuller at safety more often, and has gotten safeties Daniel Sorensen and Rashad Fenton more involved in the back end alongside cornerbacks Breeland and Charvarius Ward. Thanks to some savvy scheming, plenty of flexibility among its top coverage players, and an ascending pass-rush group featuring a now-healthier duo of Frank Clark and Chris Jones, the Chiefs finished the regular season as the league’s sixth-best pass defense by DVOA, and that performance in coverage has carried over to the postseason.

With a strong coverage unit and and improving pass rush, this Chiefs defense is built to protect a lead (when teams are forced to pass more often), which fits well with K.C.’s buzz-saw offense. But with Mahomes and Co. going up against a strong 49ers defense on Sunday, game script could be crucial to the Chiefs’ defensive performance. If San Francisco can jump out to an early lead or at least keep the game close, Shanahan has shown that he’s not afraid to lean hard on the run game. Combine the 49ers’ brilliant play-calling guru (who has dialed up a run on 71 of his past 88 plays) with the team’s dynamic running backs group, led by Raheem Mostert, and San Francisco would be perfectly happy running the ball 50 times on Sunday.

Kyle Shanahan’s #49ers run game combines incredible multiplicity with pre-and post-snap motion to confuse and/or freeze defenders on just about every play. I drew up a few examples! pic.twitter.com/NsHDDLX4zl — Danny Kelly (@DannyBKelly) January 28, 2020

That puts a ton of pressure on this Kansas City offense to force the 49ers to pass. “Nothing’s tougher in a game to call than when you can’t stop the run,” Spagnuolo told Sports Illustrated’s Albert Breer this week. “There are things you can adjust when it’s passing and all that. But a run game when they just come at you like this team does? You just have to bear down and it becomes man against man.”

The Chiefs’ run defense was its clear vulnerability this season, finishing 29th in DVOA while surrendering 4.9 yards per carry (fourth worst). Kansas City did improve in that area down the stretch, with Clark and defensive end Tanoh Kpassagnon combining to set stronger edges with interior defensive linemen Mike Pennel, Derrick Nnadi, and rookie Khalen Saunders clogging up the middle. That group surrendered just 93.6 yards per game in its last eight games (including the postseason), a clear improvement over the 148 yards per game they gave up in the first 10 weeks of the season. But while Kansas City did well to stifle the Titans’ outside-zone-heavy scheme last week, the 49ers are a different challenge altogether―with far more speed at running back and a full suite of counterplays to take advantage of an overly aggressive defense that loads up to stop any specific run. Shanahan is the master at picking the perfect counterpunch to catch a defense off guard.

Even more worrisome for Kansas City is that its defense has really struggled against teams running out of I-formation looks this season, a formation that just so happens to be the 49ers’ bread and butter. Kansas City had problems defending teams that used a lot of pre-snap motion this year, too, according to Sharp Football Analysis, with their defensive success rate dropping by 11 percentage points (from 59 percent to 48 percent) when teams send a guy in motion. Guess which team uses the most pre-snap motion in the NFL. (It’s the 49ers.) Kansas City won’t want to sacrifice its increasingly effective pass coverage in favor of selling out to defend the run, but it’s easy to see this game coming down to the question of whether or not the Chiefs can slow down the 49ers’ devastating run game.

The Chiefs defense went into the AFC championship game brimming with confidence (with Clark going so far as to say that the then-red hot Henry was “not hard to hit”). But that group surprised a lot of people by backing up all that talk, helping dispatch a Tennessee team whose ground game had looked unstoppable. After suffering through two weeks of what’s probably felt like nonstop praise for Shanahan’s superb ground attack, the Super Bowl probably has an air of familiarity for Chiefs defenders. That gives them the perfect chance to silence all the doubters for good.