AP photo by Adrian Kraus / Head coaches Andy Reid of the Kansas City Chiefs, right, and Sean McDermott of the Buffalo Bills greet each other after their Oct. 19 game in Orchard Park, N.Y. The Chiefs beat the Bills 26-17.

KANSAS CITY, Mo.— A decade after firing Sean McDermott as his defensive coordinator, Kansas City Chiefs coach Andy Reid will stare across the field inside Arrowhead Stadium on Sunday and see his protégé trying to spoil his hopes of a Super Bowl repeat.

Funny thing: Even after firing him, Reid suspected deep down that McDermott was destined for big things.

"Very organized, very smart and very tough," is how Reid described the Buffalo Bills' fourth-year head coach. "He came from a coaching family — his dad was a heck of a coach. Sean just kind of picked up right from there. Very solid, very good."

In fact, downright exceptional.

McDermott has the long-suffering Bills playing in their first AFC championship game since beating Kansas City on Jan. 23, 1994, when they advanced to their fourth straight Super Bowl — and fourth straight loss in the NFL title matchup. This season, they have won 11 of their past 12 games since losing to the Chiefs on Oct. 19, defeating the Indianapolis Colts in the wild-card round of the playoffs and the Baltimore Ravens in last week's divisional round.

Now the second-seeded Bills (15-3) will take on the top-seeded Chiefs (15-2), who are hosting the AFC title matchup for the third year in a row. The 6:30 p.m. game will be televised by CBS.

"He deserves coach of the year, man," Reid said of McDermott. "He's taken a franchise there, both he and his general manager (Brandon Beane) have put this thing together with some bold moves and production now. I think he's done a tremendous job.

"What a great thing for the NFL and for Buffalo. They love football in Buffalo, and he's really done a nice job with that whole program."

It neatly parallels what Reid has done in Kansas City.

Both coaches took downtrodden organizations and quickly built them into juggernauts. Both have bright young quarterbacks, the Bills with 24-year-old Josh Allen and the Chiefs with 25-year-old Patrick Mahomes. Both have surrounded them with playmakers, such as the Bills' Stefon Diggs and the Chiefs' Tyreek Hill and Travis Kelce. And both have built defenses that not only complement two of the best offenses in the NFL but are capable of clinching wins under pressure, as each did last weekend.

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AP photo by Jeffrey T. Barnes / Kansas City Chiefs quarterback Patrick Mahomes, left, greets Buffalo Bills counterpart Josh Allen after their Oct. 19 game in Orchard Park, N.Y.

McDermott never harbored any animosity toward Reid, who fired him from his Philadelphia Eagles staff on Jan. 15, 2011. Instead, he went to the Carolina Panthers and over the next five years honed his craft and built his reputation to the point that the Bills — who at the time had not made the playoffs since the 1999 season — were willing to give him a shot in charge.

Buffalo reached the wild-card round in 2017 and again last season before ending long droughts on multiple front with its success this season.

"It's always an honor to go up against great coaches, and Andy will be a Hall of Fame coach here in the future sometime down the road," McDermott said. "I've learned a lot from Andy in my time with him in Philadelphia, so I have a tremendous amount of respect for him and his family, the way they helped guide me then and still do today."

As for this game, it avoided losing some of its luster when the matchup of young star quarterbacks was retained.

Mahomes sustained a concussion during last week's win against the Cleveland Browns, exiting in the third quarter as veteran backup Chad Henne and the defense sealed a 22-17 victory. However, Mahomes took first-team reps all this past week during practices, and the MVP of the 2018 NFL season and last year's Super Bowl was cleared to play by team doctors and an independent neurologist on Friday.

"You have to take it day by day. I think that's the biggest thing," Mahomes said. "You can only control what you can control. Try to come in with a positive attitude, make myself better, prepare myself like I was going to play, and luckily enough, I didn't have any symptoms and now I can play."

Both quarterbacks direct offenses far more likely to take to the air than go to the ground, but Buffalo is leaning extra heavily on Allen's arm these days. Last week against the Ravens, the Bills called just one running play in the first half and finished with 16 carries, including four kneel-downs by Allen, for 32 yards in their lowest rushing output since a game against the Minnesota Vikings in 2002.

"We're not going to change who we are," Allen said. "It's the biggest game because it's the next one, but we understand that we don't have to be anyone different than who we are."