ORCHARD PARK, N.Y. -- When a sliding offense meets a plummeting defense Sunday at Arrowhead Stadium, something will have to give.
The Kansas City Chiefs' offense had been firing early this season. Through Week 5, that group scored the most offensive points per game (30.2) and gained the second-most yards per game. Since Week 6, the Chiefs rank 22nd in offensive points per game (18.2) and 21st in yards per game (327.6).
The decline of the Buffalo Bills' defense over about the same period of time has been even more severe.
Through Week 4, the Bills gave up the fewest points per game (13.5) and eighth-fewest yards per game (306.0). Since Week 5, the Bills have allowed the most points per game (32.67) and second-most yards per game (407.3) in the NFL.
The Chiefs have lost four of their past five games, and the Bills are on a three-game losing streak in which they have allowed 135 points, tied for the fourth-most by any NFL team since 1970 over a three-game span.
Either the Chiefs' slumping offense will be the perfect medicine for the Bills' defense, or Buffalo's defense will be an ideal bounce-back opportunity for Kansas City's offense.
The most baffling part about both units' struggles is that injuries have not appeared to play much of a role. The Chiefs' offensive core of quarterback Alex Smith, running back Kareem Hunt, wide receiver Tyreek Hill and tight end Travis Kelce have all played every game this season. The Bills defense has only dealt with one defensive starter, cornerback E.J. Gaines, having missed significant time over their recent downturn.
"It's a very good offense we're going to face this coming Sunday, but I think we have the guys in the room to get it done," Bills defensive coordinator Leslie Frazier said Monday. "Myself and the coaches, we've got to put together a good plan and let the guys go out and execute that plan. We've done it before; we've just got to figure out how do we get back to doing the things we were doing so well for a period of time."
The Bills have done few things right and many things wrong on defense, but one of the main areas of concern is the run defense. Buffalo's past three opponents -- the New York Jets, New Orleans Saints and Los Angeles Chargers -- have combined for 638 rushing yards and 11 rushing touchdowns.
"Same old, same old," linebacker Lorenzo Alexander said after Sunday's 54-24 loss to the Chargers. "Guys not in their gap, not getting off blocks, not making tackles when they need to. Simple as that."
At an average of 212.7 rushing yards allowed since Week 9, the Bills easily rank worst in the NFL in that category -- and it's not even close. The Lions' defense is second-worst, have given up 167 rushing yards per game since Week 9. Extending the scope back to Week 5, the Bills have allowed the third-most rushing yards per game (137.7).
The Bills' decision to trade defensive tackle Marcell Dareus to the Jacksonville Jaguars during Week 8 is a natural place to start when discussing the issues of the run defense.
In the five games that Dareus played this season for Buffalo, the Bills allowed 138 yards on 52 opponent rushes (excluding kneel downs and quarterback scrambles) for an average of 2.7 yards per carry when the former No. 3 overall pick was on the field.
When Dareus was not on the field during those five games, the Bills allowed 225 yards on 62 rushes for 3.6 yards per carry. However, in two of those games -- at Atlanta in Week 4 and versus Tampa Bay in Week 7 -- the Bills’ yards per rush was better without Dareus on the field.
In games that Dareus has not played for the Bills, they have allowed 777 yards on 145 opponent rushes for 5.4 yards per carry. That includes a Week 3 game against Denver that Dareus missed because of an ankle injury that lingered against the Falcons.
There were obvious salary-cap benefits to the Bills dumping Dareus' contract and it became clear as early as the preseason that he was not a fit for Sean McDermott's hard-nosed style of coaching. The trade made sense for the long term but in the short term, losing Dareus has generally had a negative impact on the Bills' run defense.
Buffalo's defensive problems, though, are not limited to the running game. Even though McDermott and Frazier made large-scale changes to the defensive scheme from what was seen under former coach Rex Ryan, the team has still been unable to generate a pass-rush.
Under Ryan from 2015-16, the Bills blitzed on 26.9 percent of opponent drop backs, 16th-most in the NFL, and caused pressure on quarterbacks on 26.0 percent of drop backs, 11th-worst in the NFL. The Bills sacked opposing quarterbacks on 4.9 percent of drop backs, fifth-worst.
This season, the Bills are blitzing on 26.5 percent of opponent drop backs, 17th-most in the NFL, and have caused pressure on only 21.9 percent of drop backs, second-worst in the NFL. The Bills have sacked opponents on 3.9 percent of drop backs, third-worst.
Frazier explained Monday the issue is not relegated to defensive ends Jerry Hughes and Shaq Lawson, both former first-round picks who have combined for only six sacks this season. However, he pointed to a need for improvement for Lawson in that area.
"I think he's coming along," Frazier said. "He had a real nice pass-rush on one occasion where he was able to get his hands on the quarterback's hand, basically, and get a deflection, although he ended up catching the ball. That was good to see; good to see him turn the corner, finally get to the quarterback. It's something that we want to see more of in him."