While the Rams were finally able to overcome their six-game losing streak against the 49ers and became the second team in two years to advance to a Super Bowl in their home stadium, the shocking result from Sunday’s conference title games was unquestionably what we saw in the afternoon.

After coasting to a 21-3 lead in the second quarter, the Chiefs utterly and completely collapsed against Cincinnati. The Bengals promptly rolled off 24 consecutive points to take the lead, and while the Chiefs tied the game at the end of regulation and won the coin toss, a Patrick Mahomes interception and an Evan McPherson field goal sealed a stunning trip to Super Bowl LVI for the Bengals.

We’ve seen heavy pregame favorites lose before, of course, but this has to be one of the most shocking defeats in recent memory. The Chiefs topped out with a win expectancy of 95% after building that 18-point lead, meaning they had a better chance of winning than the Bills did after either of their late touchdowns in the divisional round. Chiefs fans were frantically trying to log onto the in-stadium Wi-Fi to buy plane tickets to Los Angeles. The game felt over.

What happened? How did the Bengals claw their way back? And how did the Chiefs blow a three-possession lead and miss out on a chance to make their third consecutive Super Bowl?

Mistake after mistake for the Chiefs’ offense

Even a cat uses up its nine lives eventually, and that day came for Kansas City. The Chiefs have been the poster children in the postseason for surviving sloppy football and mental mistakes, owing to the overwhelming talent and creativity of their superstars. When they couldn’t stop Josh Allen and the Bills with the game on the line last week, the big three came through to bail them out. On a long enough timeline, they almost always seem to overcome their mistakes by producing something special when it matters.

But after jumping out to a big lead on Sunday, the Chiefs couldn’t capitalize. They made mistake after mistake, and while they were almost able to overcome those issues with a late drive, no salvation was coming. They have nobody but themselves (and the efforts of a never-say-die Bengals team) to blame. And while they didn’t do much on defense during the Bengals’ comeback, so many of the subpar plays came on the offensive side of the ball:

The Chiefs fail to score on the final play of the first half. After Samaje Perine ran away from a Charvarius Ward tackle and took a 41-yard screen to the house with 1:05 to go in the first half, pretty much everyone who watched that classic Bills-Chiefs game thought the same thing: The Bengals scored too early. With just over a minute to go and two timeouts in hand, Kansas City was in great shape to answer. Cincinnati coach Zac Taylor was certainly thinking about it, as the Bengals were trying to bleed clock on that final drive before Perine scored “too early.”

The Chiefs’ offense had been unstoppable to that point and kept it up, driving 66 yards in five plays before using its final timeout with 13 seconds left. Tyreek Hill then drew a pass interference call in the end zone, giving the Chiefs the ball at the 1-yard line with nine seconds to go. After a Mahomes throwaway, they faced a second-and-goal from the 1 with five seconds left and no timeouts.

It’s possible that the Chiefs felt they could have run two plays in five seconds, although those plays would have needed to happen very quickly. For all of Mahomes’ strengths, he’s not always the most decisive quarterback in the red zone. If we assume that they were going to have the opportunity to run only one more play or kick a field goal, ESPN’s win probability model leaned slightly toward going for it, with their chances to win jumping from 92% attempting a field goal to 93.4% going for broke and attempting to score a touchdown.

The Chiefs likely got a look they liked, but Mahomes and Hill didn’t execute it. They ran a run-pass option with an inside zone run, a slant to Travis Kelce and a swing route to Hill, who was in motion on the play. Hill was left with a huge swath of space on the left side of the field, and with Eli Apple in man coverage on the play, the oft-criticized Bengals corner was asked to run across the field and tackle Hill in space. Mahomes’ pass took Hill backward and forced him to come to a near-stop before running forward, and by the time he turned around, Apple and Trey Hendrickson were there to make a touchdown-saving tackle:

Chiefs got the look they wanted with Hill coming across the formation against Apple with that entire side of the field wide open, but Mahomes’s throw was in an awkward spot and Apple makes a great tackle. pic.twitter.com/kd2hQ3fcSX

— Bill Barnwell (@billbarnwell) January 30, 2022

B.J. Hill intercepts Mahomes. This is where the comeback really started to escalate. After the defense stiffened up in the red zone and held the Bengals to a field goal to retain an eight-point lead in the third quarter, one of Cincinnati’s other defensive additions from outside the organization made a huge play. Hill, who was acquired in August from the Giants for former first-round bust Billy Price, became the latest in a line of Bengals defenders to come up with a crucial interception.

Facing a second-and-3, the Chiefs ran another RPO, this time with stick/flat options to both sides of the field. The Bengals sent a sim pressure, with a free rusher (Vonn Bell) coming off the right side of the line and Hendrickson dropping into coverage. Instead of throwing at the space vacated by the pressure to an open Hill for an easy completion, Mahomes chose to work the left side of the field. Hendrickson was actually in the throwing lane Mahomes was trying to hit, but before the ball could even get there, Hill got in front of the ball and tipped it to himself for a pick:

Rock the Baby, @BJHill5

Watch on CBS | #BudLightCelly pic.twitter.com/F36Y3UBzSP

— Cincinnati Bengals (@Bengals) January 30, 2022

Still, though, the Chiefs usually manage to overcome interceptions. The Bengals tied the game with a touchdown and a 2-point conversion and forced another punt, but after L’Jarius Sneed stepped in front of Ja’Marr Chase to pick off of Joe Burrow, the Chiefs were back in business at midfield. Surely, this is where Kansas City would take advantage of its opponent’s mistakes, right?

Not quite. Mahomes sailed a second-down swing pass to Clyde Edwards-Helaire. On third-and-6, Hendrickson beat Orlando Brown Jr. around the edge and sacked Mahomes to end that drive. The Bengals then held the ball for more than six minutes, with Burrow scrambling twice for first downs before kicking a field goal to go up three.

After flailing their way to a total of two first downs across their first five possessions in the second half, the Chiefs finally found some rhythm on offense. After Kelce converted a third-and-2 to get to the Cincinnati 5-yard line with 95 seconds to go, the Bengals were holding on for dear life. On TV commentary, Tony Romo was even wondering whether the Bengals should have let the Chiefs score a touchdown to try to get the ball back with a chance to win the game.

(A quick aside: We know what happened, but even beforehand, this would have been a bad idea. It’s reasonable to let a team score in this situation when it’s a tie game or you have a lead of one to two points, given that a chip shot field goal will win the game, but a three-point lead gives you the chance to keep the game going with a field goal and win at the end of regulation or in overtime.)

The Chiefs were in position to have their cake and eat it, too. After a Jerick McKinnon run on first down gained a yard, the Bengals used their final timeout with 1:30 remaining. Just 5 yards away from the end zone, the Chiefs could run the clock down and score a touchdown to go up four. If everything else failed, they could kick a field goal to send the game to overtime. At this point, they strung together the worst five-play offensive sequence of the entire Mahomes era.

Mahomes melts down. When the Chiefs came back out on second down, Kelce curiously was not on the field. Let me say that again: Despite not being involved in any contact on the first-down play and getting a breather after the Bengals called timeout, Kelce, their best red zone weapon, was not on the field for one of the most important plays of the season. Instead, Blake Bell was the lone tight end. I’m not sure how or why that happened.

The Chiefs ran play-action off inside zone, but nobody was immediately open. Byron Pringle came open in the back of the end zone, but by the time he ran free, Bengals defensive lineman D.J. Reader — another one of those imports from the past two offseasons — had extricated himself from Joe Thuney. If Mahomes has a half-second more to throw, he probably sees Mecole Hardman and takes a few steps backward before lofting a pass to the back line. Instead, he pulled a 360 to escape Reader before running into Sam Hubbard for a 5-yard sack.

Third-and-goal was worse. Kelce was back on the field, and with a three-man rush, Mahomes again had plenty of time to throw. I actually can’t believe Mahomes didn’t try to hit Kelce in this initial window on his crossing route:

Third-and-goal for the Chiefs on the Mahomes fumble. He stares down Travis Kelce on this crossing route and doesn’t throw the football. I need to see this on the All-22. pic.twitter.com/kZzRPnXeen

— Bill Barnwell (@billbarnwell) January 31, 2022

Instead, Mahomes waited. He didn’t throw the ball to Pringle at the goal line or attempt a much more difficult pass to Hill streaking along the back of the end zone. From 14 yards away, Hubbard closed in on Mahomes with a straight-line dash toward the quarterback. Instead of getting rid of the football or simply going down to avoid anything disastrous happening, Mahomes tried to duck Hubbard and fumbled. This would have been one of the worst lost fumbles in NFL history given the circumstances, but the Chiefs were lucky enough to have Thuney fall on the football and for Harrison Butker to kick a 40-yard field goal, sending the game into overtime.

The Chiefs get lucky, and then they don’t. After winning the coin toss, they continued to play ugly football. On first down, they ran another RPO. Mahomes held the ball and tried to throw a quick out to Demarcus Robinson, but with Hendrickson occupying his throwing lane, Mahomes tried to loft the throw over him and sailed it. This was the best play, by far, of the sequence.

On second down, disaster nearly struck. The Chiefs worked out of empty and tried to get Mahomes an easy completion with a quick slant to Robinson. (Why they were deciding to establish their fourth wideout in overtime with their season on the line is a bit of a mystery.) Facing a slot blitz, there appeared to be miscommunication on where Robinson was going, and Mahomes’ pass went right to Apple, who dropped what would have been one of the easiest interceptions of his life.

This felt like the last respite, the moment that might spur them to suddenly click back into being the terrors we saw against the Bills. Instead, there was no respite. On third down, the Bengals showed Mahomes a window for a deep shot and took it away. Hill lined up in the slot against Mike Hilton, but after trailing Hill for 10 yards, Hilton passed off the route to Vonn Bell and turned around to play a “robber” role in the middle of the field. Mahomes took that brief window to try to find Hill on a deep over route, but deep safety Jessie Bates got over to contest the route. The ball ricocheted off a diving Hill and into the hands of Bell, who returned it to the 45-yard line. Three first downs later, the Bengals were heading to the Super Bowl.

If things break slightly differently, the Chiefs overcome those mistakes. Andy Reid wasted a timeout in the first half before challenging a third-and-1 spot; had they simply challenged the play outright, they would have had an extra timeout for that sequence at the end of the half and could have run the ball in short yardage. If Mahomes gets an extra half-second in that goal-to-go sequence at the end of the game, maybe he throws a touchdown pass. As it was, the Chiefs were sloppy in too many key moments, and the Bengals did an incredible job of shutting them down when it mattered most.

How did the Bengals’ defense do it?

The other shocking element of all of this is just how dominant the Bengals were after halftime. With their season on the line, the league’s 19th-ranked defense by DVOA suffocated the Chiefs. As The Athletic’s Sheil Kapadia noted Sunday night, the Chiefs were reduced to the worst single half of football on offense that we’ve seen in any game of the Mahomes era by expected points added. After posting a 98.0 QBR in the first half, Mahomes posted a QBR of 1.4 in the second half and overtime, per ESPN’s Seth Walder.

Somehow, after being shredded during the first half, the Bengals morphed into the ’85 Bears after halftime. How? Using the data from NFL Next Gen Stats and from charting every snap, I did my best to try to piece together how they solved the Chiefs in time to save their season and advance to the Super Bowl.

In the first half, the Bengals mostly tried to do the same things the league has done against Mahomes and the Chiefs this season, and they enjoyed virtually no success with their attempts. When they ran two-high coverages in the first two quarters, Mahomes was 11-of-12 for 141 yards and a touchdown. The Chiefs were able to slice up those coverages by throwing digs and crossers in front of the safeties and then using motion to create opportunities.

Mahomes also hit two big plays against single-high coverages in the first half; one on a deep crosser to Hill, and another on a play in which late motion by Hill took a safety out of the middle of the field and created a one-on-one opportunity for a 44-yard bomb to Hardman. The Chiefs posted an 82.4% pass block win rate during the half and mostly dominated up front. The only blemish on their record was the failure on the final play.

How did the Bengals turn things around? A few factors combined to contribute to a stunning defensive improvement:

They played more single-high coverages and lived to tell the tale. Yes, after an entire season in which the league supposedly learned that the secret to stopping the Chiefs was playing two-high, the Bengals were able to get themselves by playing more single-high coverages. They played a lot of Cover 1 Robber during the second half, a shell in which there’s one safety playing deep in the middle of the field. The other safety drops down closer to the line of scrimmage and helps coverage from the middle, where he can either get into throwing lanes or provide inside leverage for defenders dealing with crossing routes.

By my count, the Chiefs ran 12 plays against single-high safety looks in the second half and overtime. Those 17 plays netted a total of 41 yards. To be fair, things weren’t exactly going great when the Bengals stuck in two-high defenses; the 17 plays the Chiefs ran versus two-high looks netted a grand total of … 42 yards. Playing single-high coverages against the Chiefs without giving up the sort of big plays the two-high looks were supposed to take away was a huge advantage.

The shift toward a more even coverage split helped take away what had been a fruitful avenue of attack for Mahomes and the Chiefs: throws to the outside. In the first half, when Mahomes threw outside the numbers, he went 8-of-8 for 97 yards with three touchdowns. After the break, on those same throws, he went 0-for-6 with an interception. The Bengals gave away too many easy completions to the outside in the first half, but after halftime, the Chiefs simply weren’t able to make them pay for moving that second safety underneath.

Lou Anarumo got creative rushing three. Cincinnati’s defensive coordinator basically threw his blitz packages out of the playbook for this game. Outside of one five-man pressure inside the 5-yard line, the Bengals didn’t blitz once. We saw a couple of sim pressures, like the one on the Hill pick, but they abandoned any idea of sending big blitzes at Mahomes in the hopes of creating pressure.

Instead, Anarumo sent less pressure than virtually any team has sent at Mahomes in a game so far. Mahomes saw a total of 45 three-man rushes this season, or an average of about 2.4 three-man rushes per contest. The Bengals sent three-man rushes after Mahomes 15 times on Sunday, 10 of which came after halftime. Despite the idea that Mahomes would just pick those coverages apart and eventually find an open receiver, I found that those 15 plays produced only 38 net yards. According to Next Gen Stats, Mahomes was 7-of-13 for 58 yards with a pick and two sacks when the Bengals dropped eight into coverage.

In most cases, the Bengals were rushing three and then using the fourth rusher as a spy to try to limit Mahomes’ ability as a scrambler. One week after he ran seven times for 69 yards and a touchdown, he scrambled only three times for 19 yards and one first down on Sunday. This most often fell on Logan Wilson, who would begin to rush and muddle up a blocker before rolling to the middle of the field, which gave the Bengals the benefit of both having a spy on Mahomes and occupying a blocker long enough for their defensive ends to get one-on-ones against Kansas City’s tackles.

What we also saw, though, was the Bengals putting both Hubbard and Hendrickson into coverage. Often, they would either chip or just begin to cover Kelce at the beginning of the star tight end’s route before dropping into coverage as either a flat or hook defender. It’s easy to wonder why a team would “waste” one of their best edge rushers by dropping them into coverage, but this was an effective tactic in terms of taking away Kansas City’s easy completions on drag routes and in the quick game.

This tactic might have swung the game for the Bengals. As you saw from the third-and-goal clip earlier, Hubbard getting in Mahomes’ throwing lane might have taken away would-be game-winning throws to Kelce and Pringle before Hubbard strip-sacked the Chiefs quarterback. Hendrickson dropping into Mahomes’ throwing lane created a moment of uncertainty on the Hill pick and forced him to sail an easy completion on the opening play of overtime. It felt like Mahomes was unsure of what he was seeing at times during the second half.

Dropping eight into coverage also gave the Bengals the ability to double both Hill and Kelce while forcing Mahomes to find another receiver. On third-and-3, for example, they rushed three and managed to bracket both of Kansas City’s star defenders long enough for the three-man rush to get home and sack Mahomes. Most teams wouldn’t be brave enough to run a 3-1-7 alignment out on third-and-3, but the Bengals were confident that the Chiefs weren’t going to be either able or interested in running the ball:

Chiefs run mesh on third-and-3. Michael Thomas (31) comes out of the huddle behind the NT and ends up 18 yards deep as the single high safety by the time the snap actually takes place. Bengals have Hill + Kelce doubled and Mahomes eventually gets sacked. pic.twitter.com/p3TdRJMiYE

— Bill Barnwell (@billbarnwell) January 31, 2022

For what it’s worth, while the natural criticism for any Reid loss is that his team didn’t run the ball enough, I’m not sure that’s the case here. During the second half, the Chiefs faced a first down versus a look with two high safeties 11 times. They ran the ball on six of those 11 plays and Mahomes scrambled on a seventh. They actually netted 43 yards on those 11 plays, which is impressive given that their other 23 plays netted only 40.

The Bengals got more pass pressure. Even while rushing three, they had more success getting after Mahomes in the second half. At the same time, Cincinnati’s offense did a much better job of protecting Burrow after halftime. The pressure rates generated by each team show that a lopsided first half turned into a much closer battle in the second:

Mahomes posted a 4.6 QBR when under pressure against the Bengals, going 2-of-4 for 18 yards with four sacks and a fumble. A couple of those pressures were on the line, but most were on Mahomes as he scrambled and maneuvered to find open receivers. His ability to make magic happen on the fly is part of what makes him incredible, but it can also lead to ugly halves like the one we saw Sunday.

The Bengals started getting more aggressive with their coverage. This one is more anecdotal, but I saw multiple examples of it during the game, and I feel confident that it would be borne out if we could ask the Bengals under oath. It became clear as this game went on that the referees had no intention of calling anything but the most obvious penalties, and after halftime, the Bengals got more aggressive in terms of challenging Kansas City’s receivers. (For one example, look at Kelce getting grabbed and spun around on second-and-6 with 1:50 to go.) I don’t want to say they were getting away with penalties, but I suspect that they would have been flagged more often if this had been, say, Shawn Hochuli’s crew instead of Bill Vinovich’s.

If this sounds like I’m accusing the Bengals of something untoward, that’s not the case. Defensive backs should do everything they can get away with in coverage, especially in a league in which offensive players are granted so many advantages by the rules. The Chiefs were snatching and grabbing even more aggressively than the Bengals were; Sneed notably grabbed Chase’s jersey from behind to help slow down the wideout on that interception in the fourth quarter. There are the rules on paper and the rules that are being administered by the referees in an actual game. The Bengals were smart to play to the limits of the game the referees were calling, although they were lucky by any measure to get away with a late hit on Hardman.

There were other small factors in the second half. The Chiefs dealt with communication issues on offense, which cost them on a couple of third downs. Mahomes seemed to fall in love with lofting and lobbing passes to the sideline, and it seemed like he was almost too fine in terms of threading his throws at times. There were some drops and some poorly thrown passes.

More than anything, though, the Bengals adapted and survived. With their playoff lives at risk, Hendrickson & Co. simply out-executed the Chiefs to help fuel a legendary comeback. Virtually no one expected the Bengals to be in the postseason before the season. Few expected them to beat the top-seeded Titans, and even fewer thought they had a shot against the Chiefs. By the time they went down 21-3 on Sunday, I suspect that there were even Bengals fans who were resigning themselves to their fate. The Bengals have repeatedly proved that it’s foolish to count them out. After a stunning second half, nobody is taking them lightly anymore.