KANSAS CITY, Mo. >> Marcus Mariota did everything to help the Titans advance in the playoffs, throwing two touchdown passes, running for crucial first downs and providing the spark needed to rally from a 21-3 halftime hole.

Heck, the Saint Louis alum even caught one of his own TD passes.

It all added up to a heart-stopping 22-21 victory over the Kansas City Chiefs today, the first postseason win for the Titans in 14 years and one that will provide some relief — for the week, at least — for embattled coach Mike Mularkey and his remarkable bunch of underdogs.

“Special,” said Mariota, whose 205 yards passing included the go-ahead 22-yard strike to Eric Decker with six minutes left. “I’m part of a great team. I’m part of a group of guys that really believe in each other. And it’s something special.”

Now, the Titans will find out Sunday whether they’re headed to New England or Pittsburgh next.

Derrick Henry added a career-high 156 yards rushing and another score for Tennessee (10-7), while a defense fileted by Alex Smith and the Chiefs (10-7) in the first half pitched a shutout in the second half — dooming the Kansas City franchise to another humiliating postseason defeat.

The Chiefs haven’t won a home playoff game since January 1994.

“I’m in shock,” Smith said. “The swing at halftime to the final whistle, definitely a shock. Yeah. Didn’t feel like we played up to how we’re capable of playing and that’s disappointing.

Smith threw for 264 yards and two touchdowns , but most of that came before halftime. He couldn’t get going in the second half and misfired on fourth-and-9 at the Titans 44 with just over two minutes to go, denying the Chiefs a chance for Harrison Butker to kick a go-ahead field goal.

Adding to the depression? Henry appeared to fumble as Tennessee tried to run out the clock.

The Chiefs’ Derrick Johnson picked up the ball and returned it for a touchdown with 1:47 to go, and the crowd went wild as fireworks shot off over Arrowhead Stadium. But a replay clearly showed Henry down, the call was overturned and Tennessee succeeded in running out the clock.

“Grit. It’s just grit,” Henry said. “We told them we’ve got 30 minutes left, all we’ve got to do is play our game. Execute the plays and everything will take care of itself.”

In the first half, the Chiefs looked every bit the team that had won four straight in convincing fashion, and the Titans looked every bit the team that backed into the playoffs.

Kareem Hunt, the league’s top rusher this season , plunged in from 1 yard for a 7-0 lead. Smith hit Travis Kelce, who later left with a concussion, with a 13-yard touchdown pass. And he added another TD toss to Demarcus Robinson on the final offensive play for a 21-3 lead at the break.

“We were feeling good,” Johnson said. “We came in 21-3 and that’s all we were talking about: ‘Finish. Don’t get complacent. We have bigger goals than this game.’”

But it was the Titans who finished, and it was Mariota who led the way. He capped a 91-yard TD drive to start the second half in the bizarre fashions: Mariota threw a TD pass to himself.

His throw to the end zone was batted right back at him by Darrelle Revis, and Mariota hauled it in and dived for the goal line. It was the first time a player has thrown a TD pass to himself in the playoffs, and the first time in any game since the Vikings’ Brad Johnson during the 1997 season.

“Right place, right time,” Mariota said with a smile.

Tennessee nearly squandered its momentum when Adoree Jackson fumbled a punt, but the Chiefs were unable to pick up a first down and Butker knocked a 48-yard field goal off the upright. And the Titans capitalized when Henry rumbled nearly untouched 35 yards for a touchdown a few minutes later.

The Chiefs’ offense had been rendered impotent by that point, unable to move the ball after Kelce left with a concussion in the first half. And the Titans blanketed Tyreek Hill whenever he touched the ball, and they stacked the box to slow Hunt down in obvious rushing situations.

Finally, the Titans pulled ahead on Mariota’s strike to Decker, and that led to more controversy from the officials. Tennessee went for a 2-point conversion and a field-goal edge, Mariota fumbled as he was getting sacked and Frank Zombo scooped up the ball for two points the other way.

But the officials had blown the play dead, ruling Mariota’s progress had been stopped, and the Titans retained the slimmest of margins — one that would stand up to the final whistle.

“I feel really good around our football team,” Mularkey said. “I know what I’m going to get from them every week. That’s a good feeling, knowing how they’re going to come out, no matter what.”

OFFICIAL COMPLAINTS

The Chiefs also complained about the officials blowing their whistles on a play late in the first half, when Mariota fumbled while getting sacked. He clearly lost the ball and the Chiefs picked it up, but the play could not be reviewed. Tennessee wound up kicking a field goal.

RECORD RALLY

Only two road teams have rallied from at least 18 down to win a playoff game in NFL history. The Cowboys came back from 21-3 in the first half to beat the 49ers 30-28 in December 1972, and the Lions came back from 27-7 in the second half to beat the 49ers in December 1957.

KELCE HURT

Kelce sustained his concussion on a wicked blow from Titans S Johnathan Cyprien late in the first half. Kelce, who had four catches for 66 yards, lay stunned on the turf for a moment before wobbling to his feet. Trainers quickly took him to the locker room and he did not return.

UP NEXT

The Titans’ opponent in the divisional round will be decided Sunday. If the Jaguars beat the Bills in their wild-card matchup, Tennessee heads to New England to face the No. 1 seed. If Buffalo wins, the Titans head to face No. 2 seed Pittsburgh.