On New Year's Eve in Denver in 2017, the Chiefs handed the keys to Patrick Mahomes for the first time. But just briefly.

Having already secured their spot in the postseason, Mahomes was offered his first career start. He won. Threw for nearly 300 yards. Generated a game-winning drive.

This isn't that.

On Sunday, in their 2019 regular-season finale, the Chiefs will play to win. In other words, they'll use the full allotment of their starters.

Why? Not everything has been decided. While the Chiefs have clinched their place in the postseason via their fourth straight AFC West title, their seeding remains in doubt.

The Chiefs are currently the third seed in the AFC. The Baltimore Ravens have clinched homefield advantage throughout the playoffs. The New England Patriots are No. 2, but that's where things could still change. If the Patriots lose at home to the 4-11 Miami Dolphins Sunday — a game that also kicks off at noon -- the door opens for the Chiefs to slide into the second spot, which, of course, carries a first-round bye.

That's a big if.

But it's enough for the Chiefs to go all-out Sunday when they play host to the Chargers at Arrowhead Stadium.

"There are things going on here," Chiefs coach Andy Reid said. "We have to take care of business. You never know in this business."

The Chiefs could also still fall to the fourth seed if they lose and the Houston Texans beat the Tennessee Titans later Sunday afternoon. That would give both teams the same record, with the Texans holding the head-to-head tiebreaker.

Arguments can — and will — be made analyzing the importance of the three-seed in comparison with the four, given they both must play on wild card weekend and both receive home games. But the third seed does guarantee avoidance of the potent Ravens until a potential AFC Championship game.

The Chiefs control just one piece of the entire scenario, and they will do their best to do just that — control it. They won't turn to their backups Sunday in hopes of resting their starters. It will be Mahomes under center.

He brings momentum. The Chiefs have an opportunity to carry a six-game streak into the postseason. They've played some of their best football in the last month.

Reid's decision isn't influenced by that, instead swayed purely by the absence of a locked-in seed. "I haven't gotten to that," Reid said of riding momentum into the playoffs.

Not that momentum wouldn't be an attractive bonus.

"We're still building. I think that's the biggest thing," Mahomes said. "I know we're at the end of the season, but I feel like every single week you can see this team is getting better, and we want to have that momentum of going out there and playing our best football going into the playoffs.

"We understand the Chargers are a really good football team, and we know it's going to be a great challenge, so we're going into it with the mindset we've had the past few weeks of playing our best football."