PITTSBURGH — Andy Reid donned a Santa Claus suit in a giddy Kansas City Chiefs locker room on Christmas Day, then handed his team a present it increasingly looks like it deserves: home-field advantage throughout the AFC playoffs.

How Reid managed to slide into the costume so quickly after Kansas City’s clinical 29-10 victory over the reeling Pittsburgh Steelers to lock up the top seed in the AFC for the fourth time in seven years is a mystery (though he hinted there’s an elf involved).

How Reid’s team manages to pull away from the pack year after year is not.

A lot of Patrick Mahomes. A dash of Travis Kelce. A splash of speed. A defense that quietly goes about its business, even when its leader is standing on the sideline in sweatpants.

Yes, it has been ugly — by Kansas City’s lofty standards — at times while the Chiefs have chased a third consecutive championship. Yet as the playoffs loom, the group that looked so vulnerable for most of the season suddenly seems to be rounding into form.

And the road to the Super Bowl will once again go through Arrowhead Stadium. Just the way the Chiefs like it.

“Getting the No. 1 seed is important,” Mahomes said after throwing for 320 yards and three touchdowns. “It’s like winning a playoff game.”

Even if how the Chiefs locked it up didn’t exactly feel like one.

Kansas City (15-1) spent three hours toying with the Steelers (10-6) like a cat batting around shreds of leftover wrapping paper. The Chiefs raced to an early 13-point lead and were never really threatened by Pittsburgh, which has dropped three in a row to see its chances of capturing the AFC North take another hit.

“That sucked, to be blunt,” Steelers Coach Mike Tomlin said.

It often does when Pittsburgh is on one side of the line of scrimmage and Mahomes is on the other. Mahomes is now 4-0 against the Steelers with 17 touchdowns against just one interception. He connected on first-half scoring tosses to Xavier Worthy and Justin Watson and added a history-making 12-yard touchdown flip to Kelce to seal it in the fourth quarter.

The grab was the 77th scoring reception of Kelce’s career, breaking a franchise record set by Hall of Famer Tony Gonzalez. The 35-year-old Kelce celebrated by dunking the ball over the goal post, a nod to Gonzalez’s signature move. The gesture drew a 15-yard penalty for unsportsmanlike conduct, though it hardly mattered. Harrison Butker made the longer extra point and the Chiefs were firmly in control.

“It’s just showing Tony some love,” Kelce said with a laugh on the day he joined Gonzalez and Jason Witten as the only tight ends to reach 1,000 receptions. Kelce finished with eight catches for 84 yards while playing for an offense that is starting to get its swagger back.

The defense wasn’t bad either, even with five-time Pro Bowl defensive end Chris Jones sidelined by a calf injury. Jones’ teammates hardly looked gassed while playing for the third time in 11 days.

“It was tough,” cornerback Trent McDuffie said. “I mean, three games in 11 days is crazy for anybody. But I thought we handled it very well.”

The Steelers did not. Pittsburgh went 0-3 during the span, a brutal stretch against Super Bowl contenders Philadelphia, Baltimore and Kansas City in which the Steelers looked outclassed.

Perhaps more troubling than the losses is the way they played out. Pittsburgh lost each contest by at least 14 points and could find itself starting the postseason on the road after playing fast-and-loose with the two-game division lead it enjoyed just three weeks ago.

“I think that there’s highs and lows in every season,” Pittsburgh quarterback Russell Wilson said after throwing for 205 yards with an ill-timed pick in the end zone in the first quarter. “We’ve got to make sure that we end this last game on the right footing and right belief.”

That hasn’t been an issue in years in Kansas City. Not with Mahomes at the controls. He spread his 29 completions to eight different players, including a career-best eight to Worthy and four to Hollywood Brown, whose return from injury has given the Chiefs another playmaker in what is starting to look like another stacked deck.

“We’re playing, especially offensively, our best football of the year,” Mahomes said.

Looks like it. The two-time MVP hardly bothered by the ankle injury he suffered against Cleveland, throwing touchdowns to cap Kansas City’s first two drives. And while the Steelers drew within 13-7 and 16-10, they never had the ball with a chance to take the lead in the second half.

Instead, the Chiefs — who spent most of the first three months of the season squeaking by most weeks — zoomed away with the No. 1 seed and several weeks to rest before a bid for a three-peat that certainly looks doable.