Sunday's matchup between the Kansas CIty Chiefs and Oakland Raiders was supposed to be a showdown with big AFC West implications.

The Chiefs showed up, but the Raiders didn't.

In a game flexed to a more desirable late-afternoon kickoff, Kansas City took advantage of numerous Raiders mistakes, including two first-half interceptions thrown by Oakland quarterback Derek Carr, to jump out to a 21-0 lead and win 40-9.

"It was a pure team win," Chiefs coach Andy Reid said. "All three phases contributed, which is important at this time of the year."

The Chiefs (8-4) took command of the AFC West, with a two-game lead over the Raiders (6-6) with four games remaining in the regular season. While the Chiefs control what happens to them in the final month in terms of the overall postseason picture, the players weren't taking Sunday's win for granted.

"We've just got to keep winning and keep getting better," linebacker Reggie Ragland said. "December is the most important. One game at a time."

Rookie wide receiver Mecole Hardman agreed.

"We just want to win out and win our division," Hardman said. "That's key — win our division and get to the playoffs. We've got a bigger goal in mind, so we've got to take it one game at a time and go from there."

What the Chiefs did to the Raiders this season cements their division dominance. They swept Oakland for the second consecutive season, and since falling behind 10-0 in Week 2, the Chiefs have now outscored the Raiders 68-9 in the last seven quarters. Kansas City's victory also represented its 65th in the storied Chiefs-Raiders series, their most regular-season wins against any foe.

The Chiefs turned in a disciplined, mistake-free performance Sunday with no penalties, marking just the third time in team history they completed a game without committing an infraction.

"Just the fact of not having the penalties really on either side of the ball," Reid said. "You can do some good things if you do that, and then you're productive in the red zone. Normally, good things happen."

The last time the Chiefs didn't record a penalty in a game came on Dec. 8, 1974 in a 7-6 loss to the Raiders. The first time in team history was Oct. 2, 1966 in a 29-14 loss to Buffalo.

Rookie safety Juan Thornhill electrified this Sunday's win with an interception returned for a touchdown in the second quarter. Thornhill also stuffed a Raiders fourth-and-short play in the second quarter by tackling wide receiver Trevor Davis. He finished the game with four tackles.

Veteran safety Tyrann Matheiu recorded the other interception off Carr in the Chiefs' dominant defensive effort, which also included two sacks and two quarterback hits. Carr is now 2-10 in his career against Kansas City.

The Chiefs' defense was needed for the second straight game to pick up the KC offense. Quarterback Patrick Mahomes completed 15 of 29 passes for 175 yards, his career low as a starter, and a touchdown with an interception for a 81.8 passer rating.

Kansas City's offense totaled 259 yards, 137.1 below its season average of 396.1.

The Chiefs' running game, already missing Damien Williams, saw Darrel Williams leave with a left hamstring injury in the third quarter. The Cheifs relied on LeSean McCoy and Darwin Thompson the rest of the way.

Thompson led the Chiefs in rushing with 44 yards and a touchdown on 11 carries while McCoy chipped in 10 yards and a touchdown on five carries.

"It was good to get Darwin in and get him a few reps as he continues to grow in the NFL and our offense," Reid said.

Tight end Travis Kelce paced the Chiefs' receiving group with four catches for 79 yards. Wide receiver Tyreek Hill contributed five catches for 55 yards.

Overall, the offense wasn't really needed on a day when the defense utterly stymied Carr. Defensive end Alex Okafor said the defensive rebirth began in Week 7.

"It started when Pat went out," Okafor said of Mahomes missing Weeks 8-9 with a dislocated right kneecap. "We put higher expectations on ourselves because we knew we had to do more with him being out. And now that he's back, I think we just capitalized on that momentum."

While rookie Raiders running back Josh Jacobs rushed for 104 yards on 17 carries, they quickly became a one-dimensional offense because of the Chiefs' big lead.

"All in all, a good win," Reid said.

The Chiefs have momentum heading into Week 14's matchup against their AFC nemesis, the New England Patriots, next Sunday afternoon at Foxboro Stadium.