There aren't many other ways to put it: Through the first five weeks of the 2020 NFL season, the Buffalo Bills' defense has not been good.

And that's not just by their own standards, either; they have been average to below average in nearly every facet of the game, despite a 4-1 record.

For starters, the pass defense that has been ranked among the top five each of the past two seasons has deteriorated to 24th this season. After allowing 300 passing yards just once in 2019, the Bills did so in consecutive games against the Miami Dolphins (Week 2) and Los Angeles Rams (Week 3), then allowed 297 to quarterback Derek Carr and the Raiders in Week 4.

That unit will be tested again when the Bills host 2018 NFL MVP Patrick Mahomes and the Kansas City Chiefs on Monday (5 p.m. ET, Fox/NFL Network).

The root of Buffalo's struggles against the pass is tricky to pinpoint. Several factors are to blame, starting with its overall health on that side of the ball.

Middle linebacker Tremaine Edmunds missed a game with a shoulder injury and has played through obvious pain over the past three weeks. Outside linebacker Matt Milano, Buffalo's primary pass deterrent in the middle of the field, has missed two games because of hamstring and pectoral injuries. Cornerbacks Tre'Davious White, Levi Wallace and Josh Norman have yet to all be healthy at the same time.

"Being able to play man coverage, we've struggled with that a little bit. And we've even struggled in our zones at times," Bills defensive coordinator Leslie Frazier said. "You need a combination of rush and coverage to work together in order to have success in pass defense. We haven't been able to consistently put that together yet."

Although it hasn't shown up in the team's sack numbers, the Bills have won the third-highest percentage of their pass rushes in the NFL this season at 54.7%. That said, they're not satisfied with their current standing.

Frazier mentioned second-year defensive tackle Ed Oliver, who hasn't been as impactful in Year 2 as he was during his rookie season. Oliver has worked his way through a knee injury early in the season and against Kansas City plans to ditch the brace he has been wearing.

"I'm hoping that now his confidence level will go higher because we're going to need the best of Ed Oliver this Monday night," Frazier said. "We're going to need him in a big way. We need those splash plays that we saw him produce in the second half of last season. ... That's been absent up to this point."

The Chiefs visit at a crucial point in the Bills' season. Following a 42-16 loss to the Tennessee Titans on Tuesday, the Bills have allowed 31.3 points per game over their past four outings. For comparison, they allowed an opponent to score 28 or more points one time in 2019; three have done so in 2020.

With the reigning Super Bowl champions, who have the NFL's eighth-highest-scoring offense, coming to town, it's a priority for the Bills to figure out how to close the floodgates. They're confident they can do so.

Safety Micah Hyde brought up a three-game stretch during his first season in Buffalo (2017) when the Bills allowed an average of 212.7 rushing yards and 45 points per game. After a 54-24 loss to the Chargers in the third week of that span, the Bills turned it around to beat the Chiefs the following week, holding them to 55 rushing yards.

Hyde said he isn't sure exactly what is going wrong with Buffalo's defense, but if the Bills could snap out of that stretch in 2017, they can do it again in 2020.

"I wish I had the answers right now. I wish I did," Hyde said following the loss to Tennessee. "I feel like if I did, we could go out there and execute a little bit better, but like I said, no panic. I feel like we had a rough patch here.

"We can turn it around if we just focus, dial in and everybody do their job -- I think that's what we got away from. ... When a loss like this happens, you've got to look yourself in the mirror, the team has to look itself in the mirror and understand we're not unbeatable. The defense, we're going to get it right with a guy like [coach] Sean [McDermott] steering ship."