Following “M-V-P” chants for quarterback Josh Allen, Buffalo Bills fans continued their party scene late into the night following Sunday afternoon’s 30-21 home victory over the Kansas City Chiefs.

Blue-clad supporters first danced in the aisles during the final seconds of the team’s win. Then, more than two hours after the game, they shot off fireworks in surrounding neighborhoods, with the sparks rising high above Highmark Stadium.

For a Bills fan base haunted by quarterback Patrick Mahomes and the Chiefs in the postseason, Sunday’s celebration was almost that of winning a mini-Super Bowl.

The Chiefs, however, did not act afterward as if the stakes were the same on the other end.

KC’s players were disappointed, to be sure, following the team’s first loss of the season Sunday, which halted a 9-0 start and also marked the team’s first defeat since Christmas Day 2023.

But the Chiefs also weren’t shying from tough questions in the locker room — or shirking responsibility — for the errors that led to their first setback this season.

“You’ve been in this league long enough, you understand wins and losses happen,” Chiefs linebacker Nick Bolton said. “It’s about what you do afterwards. So you’ve got to grow — as a team, as a unit — and find ways to get better.”

For the Chiefs’ defense specifically, that will start with working to eliminate small mistakes that added up.

Buffalo Bills quarterback Josh Allen rushed for a pivotal late touchdown against the Kansas City Chiefs during an NFL Week 11 game at Highmark Stadium in Orchard Park, New York on Sunday, Nov 17, 2024.

Gregory Fisher Imagn Images KC’s defense surrendered 30 points for the first time in nearly two seasons. The last time a team put up that point total was Super Bowl LVII against the Philadelphia Eagles in February 2023.

Bolton listed a few technical errors he saw Sunday:

• The team not keeping its pass rush balanced with players in the correct spots;

• Guys blitzing from their spots too late;

• Not playing with correct leverage to keep offensive players contained. “As the game progresses,” Bolton said, “those things magnify.”

Bolton also said Sunday solidified how small the margin of error can be in the NFL — especially when facing a talent like Allen on the other side. “I think it’s eye-opening for us in terms of just, you can’t let three or four mistakes in a game lead to 16, 20, points,” Bolton said.

“So you’ve got to figure out a way to knock those out.” Chiefs safety Justin Reid said third downs stood out most to him. Buffalo converted nine of their 14 attempts on third downs, with five coming when the Bills faced eight yards or more to gain.

Buffalo Bills punt returner Brandon Codrington protects the ball from the outstretched arm of Kansas City Chiefs defensive back Joshua Williams during a Sunday, Nov. 17, 2024 NFL Week 11 game at Highmark Stadium in Orchard Park, New York. Tina MacIntyre-Yee/Democrat and Chronicle Tina MacIntyre-Yee/Democrat and Chronicle / USA TODAY NETWORK via Imagn Images “I think we get off the field on third down, it’s a totally different landscape of a game,” Reid said.

“There’s too many opportunities we had them on third-and-long, third and Josh being Josh, he makes a play.” The Chiefs have had losses serve them well before. Perhaps no better example was last season’s home defeat against the Las Vegas Raiders, which forced KC to make needed changes offensively to simplify things.

Reid said the team could gain a similar spark from Sunday’s adversity. “That’s absolutely what this needs to be. It needs to be something that we build off of,” Reid said. “It’s something that we need — a reality check for us.”

Reid said he knew coaches and teammates well enough that they would learn from the Bills loss and build from it. “We’re going to use it as a stepping stone,” Reid said, “to go where we really want to go.” The Chiefs losing their undefeated season might also re-frame the season in a way that can be productive.

Quarterback Patrick Mahomes said Sunday’s result reinforced to him that the offense needed to have more urgency, especially at the beginning of games. “And that starts with me,” Mahomes said. Cornerback Trent McDuffie, meanwhile, said the team had continued to win the past few weeks while overcoming “a few little mental mistakes” defensively.

He said a loss can be an appropriate moment to refocus. “When you’re doing good, I feel like a lot of things sometimes can almost be overlooked,” McDuffie said. “ …

So I think we can take this moment to just see who we are as a team and learn from it and continue to grow.” Even some of the Chiefs’ top performers were vowing to improve. That included cornerback Chamarri Conner, who had an interception and also finished as one of the Chiefs’ top-two graded defenders in Pro Football Focus’ preliminary grades Sunday.

Conner still stood in front of his locker while telling reporters, “I feel like I played bad,” believing he could’ve done a better job with his tackling. Buffalo Bills quarterback Josh Allen leaps over Kansas City Chiefs safety Chamarri Conner en route to a first down during a Week 11 NFL game at Highmark Stadium in Orchard Park, New York, on Sunday, Nov. 17, 2024.

Mark Konezny Imagn Images “Gonna learn from it, gonna get back in the lab,” Conner said, “and we’re gonna come back stronger.” Chiefs linebacker Leo Chenal, a few cubbies to Conner’s left, said he had a specific way he wanted to use this loss: As fuel to motivate him for the rest of the season. “Remember this feeling,” Chenal said.

“We’ve been kind of living up here a little bit. Remember the feeling and how much it hurts.”