Super Bowl LIV, more than any other Super Bowl in recent memory, brought the promise of something we’ve never seen before. In a matchup headlined by Patrick Mahomes and his impossible arm, the Chiefs’ inconceivably fast receivers, a pair of all-world tight ends in Travis Kelce and George Kittle, Andy Reid’s mad-scientist scheming, and Kyle Shanahan’s seemingly clairvoyant play-calling, there was no shortage of scintillating story lines in the two-week run-up to the game.

All of those narratives played their own parts in the Chiefs’ thrilling 31-20 win: Mahomes did hit a handful of eye-popping throws, Tyreek Hill and Sammy Watkins each streaked past San Francisco’s defense, and both Reid and Shanahan showed off their play-calling ingenuity. But in the end, the story of the Chiefs’ Super Bowl win was an oft-cited and boring cliché that’s as old as the sport: Football is won in the trenches.

Defensive Rookie of the Year Nick Bosa and the 49ers’ fearsome defensive line came out swinging from the start, repeatedly collapsing the pocket, creating pressure, and stifling a shell-shocked Mahomes. The 24-year-old signal-caller looked jittery and inaccurate in the face of San Francisco’s unrelenting rush for most of the first three quarters, missing on a handful of easy throws while struggling to find anything resembling comfort in the pocket. Just about everything that came out of his hand looked off.

Bosa led the charge for San Francisco, notching a sack, a quarterback hit, a pass deflection, and a forced fumble in the game. Those numbers don’t even do the rookie’s performance justice: He was everywhere, an omnipotent presence off the edge that repeatedly forced the Chiefs to change their entire game plan—rolling Mahomes away from Bosa’s side while drawing up plays that got the ball out of the quarterback’s hands as quickly as possible. Bosa was bolstered by the team’s primary pass-rush group of Dee Ford (one QB hit, one tackle for a loss), DeForest Buckner (1.5 sacks, three QB hits), and Arik Armstead (one QB hit). Through three quarters and change, the Niners’ game plan was working perfectly: The constant pressure had forced Mahomes―typically a deep-passing savant―to rely mostly on check-downs, screens, and quick swing passes to running backs out of the backfield.

Mahomes looked well on his way to the worst game of his NFL career when he threw his second interception with 12:05 to go in the fourth quarter, a pick that killed Kansas City’s promising drive and put the 49ers in a position to put the game away for good (this was Mahomes’s first multi-interception game in 440 days, and at that point he’d passed for just 172 yards). Trailing 20-10 and facing a 49ers offense that had moved the ball well most of the first three frames, the Chiefs found themselves with their backs against the wall. Give up another long scoring drive, and the game would effectively be over. That’s when their defense turned the tables.

San Francisco quickly pushed the ball out to its 39-yard line with a pair of Raheem Mostert runs and a 12-yard Kittle reception. But on a second-and-9 with 9:53 to go, Kansas City dialed up pressure: Linebacker Anthony Hitchens sliced through the line and into the pocket, forcing quarterback Jimmy Garoppolo to hurry his throw. He sailed it over Deebo Samuel’s head.

A false start moved the 49ers back to a third and 14 from their own 34-yard line. At the snap, defensive end Frank Clark got a great jump, quickly ducking under the block of left tackle Joe Staley to chase Garoppolo out of the pocket and force the punt.

The Chiefs offense took advantage of its defensive counterpart’s big stop, mounting a 10-play, 83-yard touchdown drive on the ensuing possession to cut the 49ers lead to 20-17 with a little over six minutes remaining. But against a San Francisco offense capable of putting together long, game-sealing drives, the comeback was far from a foregone conclusion. The Chiefs needed another stop, and this time, it was defensive end Chris Jones who delivered.

Following a 5-yard Mostert run to start the drive, San Francisco faced a second-and-5 from its own 25-yard line. Shanahan drew up a play-action look to Kittle, who got open underneath with a quick slant on the right. Garoppolo saw him and let the pass loose, but the 6-foot-6 Jones jumped up to knock the ball down and prevent what would’ve likely been an easy first down―and possibly a lot more.

On the next play, Jones created pressure again, pushing left guard Laken Tomlinson into the pocket while opening up a blitzing lane for linebacker Ben Neimann, who forced Garoppolo to toss a desperate throwaway.

Gifted another opportunity by his defense, Mahomes led the offense down the field on a seven-play, 65-yard scoring drive that culminated in a 5-yard Damien Williams touchdown catch. The Chiefs seized the lead for the first time since the first quarter, 24-20, but also left a worrying amount of time on the clock for Shanahan’s offense, which started the ensuing drive from its own 15-yard line with 2:39 to go. A 17-yard Mostert run and a pair of Garoppolo throws quickly moved the 49ers past midfield, but the Kansas City defense dug deep: On first-and-10, Garoppolo tried to find Samuel on a short whip route to the inside, but Jones jumped up and batted down another pass.

On the next play, Jones did it again, using his hands to get a piece of a throw intended for Emmanuel Sanders. Nickelback Kendall Fuller knocked down the impeded pass to force a pivotal fourth-and-10 that would ultimately decide the game.

Swooping left and around Jones, Clark notched a 9-yard sack of Garoppolo that put the exclamation mark on the Chiefs’ improbable defensive stand.

Two players later, Kansas City running back Damien Williams got loose for a 38-yard touchdown to truly seal the victory, pushing the lead to 31-20, the game’s final score.

Super Bowl LIV was defined by alternating surges from two defensive lines. For three quarters and change, San Francisco’s hounding front four of Bosa, Buckner, Armstead, and Ford controlled the action, holding Mahomes in check while helping force two crucial turnovers. The tide turned in the fourth, though, as the 49ers’ lack of depth began to show up. With key reserve linemen D.J. Jones, Damontre Moore, Ronald Blair, and Jullian Taylor all on the injured reserve, San Francisco’s pass-rush appeared to lose some punch―and Kansas City adjusted by keeping more guys in to block, at times―helping Mahomes find his groove and leaving a nightmare start in the rearview mirror. Mahomes passed for 141 yards, two touchdowns, and a pick in the final frame to help put the Chiefs back in front.

As San Francisco’s pass-rush group faded, Kansas City’s defensive front got stronger. Garoppolo crumbled under the pressure, completing just three of 11 passes for 36 yards and an interception over the game’s final 15 minutes. After taking a 10-point lead, the Niners’ next three drives ended in punts, opening the door for the Chiefs offense and the team’s eventual comeback.

Mahomes turned a disastrous start into a Super Bowl MVP and cemented his spot in NFL lore by leading the Chiefs back from a 10-point fourth-quarter deficit in a title game. He wouldn’t have had the chance to work his magic without a late-game flourish from his team’s swarming, relentless defensive front.