With a 21-3 halftime lead and Alex Smith authoring one of the great first halves in postseason history, the Kansas City Chiefs’ five-game postseason losing streak at Arrowhead spanning 24 years appeared to be over. So too did Mike Mularkey’s tenure as Tennessee Titans coach.

Then something strange — seemingly countless things, really — happened. The Titans scored 22 unanswered points and stunned the Chiefs for their first playoff victory in 14 years. They'll live to fight another week, either next Saturday in Foxborough or Sunday in Pittsburgh.

There was the second-half resilience of Mularkey’s Titans. The unfathomable choking by Reid’s Chiefs. The incompetence of referee Jeff Triplette’s crew. The opener to wild-card weekend had a little bit of everything.

But we’re focusing on the contrast of two coaches.

Mularkey appeared to be a dead man walking at halftime, when Marcus Mariota was struggling in a stagnant offense that had managed only 127 yards. Mariota threw an interception to Marcus Peters that was equal parts awful decision and play design. Testing Peters — the NFL’s dominant takeaway artist over the past two seasons — was a bad idea, but multiple targets running routes in the same dangerous vicinity didn't give the play a great chance to succeed.

Meantime, Reid and offensive coordinator Matt Nagy put on a play-calling clinic in the first half, with Smith completing 19-of-23 passes for two touchdowns — with two of the incompletions being blatant Tyreek Hill drops. The Chiefs were scheming their playmakers open; the Titans' scheme looked, as it had most of the season, broken.

Then Chiefs tight end Travis Kelce was ruled out with a concussion, which he suffered late in the midst of an excellent first half for the coverage-dictating tight end, and somehow Reid forgot about NFL rushing champion Kareem Hunt.

That happened around the same time that Mularkey remembered that he dubbed his offense “exotic smashmouth” for a reason. Mariota is best when he’s allowed to use his legs and Derrick Henry, finally in a feature role thanks to DeMarco Murray being inactive with a knee injury, is a 240-pound downhill destroyer.  

And things started to click on the opening series of the third quarter for the Titans, who marched 91 yards on 15 plays, capped by one of the strangest touchdowns in NFL history.

Mariota, rolling to his left on 3rd-and-goal, tried to find Corey Davis in the end zone. Except it was batted down by a leaping Darrelle Revis, and the deflection went directly back to Mariota, who dove for the pylon and became the first quarterback ever to catch a touchdown, never mind his own, in the postseason. That made it Chiefs 21, Titans 10.

Following a three-and-out, the Chiefs' Harrison Butker missed a 48-yard field goal. The Titans had gifted them great field position at the Kansas City 28-yard line with a muffed punt, but the Chiefs couldn't take advantage.

A long Titans touchdown drive by the Titans followed and cut the lead to 21-16. Mularkey curiously opted to go for his first of two failed two-point tries that would make for some extra late-game drama, but the momentum had completely changed as the fans at Arrowhead were bracing for more playoff heartbreak.

Another failed possession by Reid’s Kelce-less (and essentially Hunt-less) offense and the Titans took over at their 20. And we should add that Mularkey's top lieutenant, defensive coordinator Dick LeBeau, deserves a ton of credit for ratcheting up the aggression and shutting down Smith and Co. after the break.

Mariota converted all three third downs and Derrick Henry continued battering a gassed Chiefs ‘D,’ setting up what would be the game winner: a 22-yard strike from Mariota to Eric Decker on a deep post. Decker had been a detriment up until then with a pair of drops, and his redemption came one play after one of Mariota’s only second-half mistakes, when he missed a streaking Davis heading down the opposite sideline uncovered.

But the damage was done. Titans 22, Chiefs 21.

The Chiefs took over with a little less than six minutes remaining, only needing a field goal thanks to Mularkey’s ill-fated conversion attempts. But they advanced barely into Titans territory before Smith’s fourth-and-9 heave down the deep middle grazed just off the outstretched arms of Albert Wilson.

That's right, Smith went for it all on fourth-and-9, a fitting end to his spectacular reinvention of himself in a career Year 13. But where was Hunt (one touch on the final series) and why didn't Reid, knowing he was in four-down territory, try and make it more reasonable on third down, when Smith was sacked on a slow-devloping play?

Reid and Nagy, not Smith, deserve the blame for another Chiefs postseason meltdown. Hunt inexplicably received just five carries after halftime despite the huge lead. The Chiefs, unlike Tennessee’s game-changing halftime adjustments, had no answer after losing Kelce.

And Mularkey and Mariota, while not perfect, deserve immense credit for spearheading another miraculous Titans playoff finish. Mariota, clearly benefiting from Mularkey’s second-half tailoring with increased up-tempo and designed quarterback runs, was 12-of-18 for 133 yards and three total touchdowns after halftime. Mariota's improvisation in and out of the pocket confounded a Chiefs 'D' missing its best interior disruptor, Chris Jones, who suffered a knee injury on the first play of the second half.

Mularkey, despite the big deficit, remained committed to Henry, who finished with 12-156-1 — with 114 of those yards coming in the second half.

And what once looked like a coaching clinic put on by the Chiefs ended with Mularkey at least temporarily saving his job, while Reid's Chiefs, now 1-4 in the postseason, head into an offseason of uncertainty again wondering what might have been.