Here are five things to watch on Sunday:

1. Chiefs run defense  (particularly on first down)

There is no secret on where the Chiefs have struggled over the past three games. Against the Seattle Seahawks, Oakland Raiders and Denver Broncos, the Chiefs allowed 597 yards rushing and lost two of those games.

Diving even further into some season numbers, the Chiefs have allowed 5.47 yards per rush on first down, which ranks as worst in the NFL, and it's allowing offenses an easier opportunity on second and third down to move the chains.

Chiefs coach Andy Reid spoke about the issue of tackling this week.

"You're going to go through ups and downs and you've got to work through those," Reid said. "One of those is our tackling right now so we will do everything we can without going live.

"I always go back to the techniques, fundamentals, angles – those are things you can work on and we will do that. The one thing about this crew here, this football team, is they will work on whatever seems to be a negative to try to fix that problem."

The Chiefs face a Cardinals offense on Sunday that has really struggled to run the football this season. They have averaged just 3.1 yards per carry (worst in NFL) and just 74.8 yards per game (second worst in the NFL).

To make matters even more difficult for the Cardinals, starting running back Andre Ellington, who has carried the ball 70 percent of the time for the Cardinals this season, will be a game-time decision as he deals with a hip-pointer injury. 

The Chiefs run defense vs. the Cardinals rush offense is a matchup of two areas both of these teams have struggled in; the winner of this battle might get the edge in this game.

2. Cardinals quarterback Drew Stanton's accuracy

If the Chiefs can find success with their rush defense on first down, they can force the Cardinals offense, led by quarterback Drew Stanton, into third-and-long scenarios and give itself a shot at making a game-changing play.

Earlier this week Cardinals coach Bruce Arians spoke of Stanton, who is 4-3 as a starter this season in place of the injured Carson Palmer.

"He's working on his accuracy," Cardinals coach Bruce Arians said of Stanton. "He's had a couple balls that got away from him. We didn't turn the ball over early in the year and we've turned it over three or four times in the last two weeks so that's the thing that's hurting us."

Stanton has completed 55 percent of his passes with six touchdowns and five interceptions in seven games for the Cardinals this season.

The Chiefs defense has only forced five interceptions this season, but Reid said they've been close to more recently.

"Sometimes when you get to this point and you haven't had a few, you press a little bit," Reid said of getting interceptions. "You saw where we had the ball in our hands a couple of more times this past week [vs. Denver].

"We need to get one, then those normally snowball in your direction, but we're in pretty good position. We just need to make sure that we focus in and squeeze the football."

When you face a quarterback who has struggled with his accuracy, the chances of getting an interception are better and Reid explained how the Chiefs defense, which is primarily known as a press-man coverage team, doesn't always lend itself to getting interceptions in that one particular look.

"You probably get more actual interceptions when you're not in man coverage in a press look but when you're off," Reid said. "We've had opportunities. We just have to take advantage of them. That's something our guys will work on."

3. Containing Cardinals defensive lineman Calais Campbell

On the other side of the ball, the Chiefs offensive line will have their hands full with Cardinals defensive lineman Calais Campbell (No. 93).

"He's a mountain of a man, just looking at him, and he plays like it as well," Chiefs quarterback Alex Smith said. "He does a good job. For as tall as he is, he plays with great leverage and does a great job batting balls down."

Campbell is Pro Football Focus’ No. 3 rated 3-4 defensive end in the NFL this season, and he leads a Cardinals front seven that has 18 sacks since Week 10, which ranks third in the NFL during that span.

"He's playing at a high level right now and he's someone that we have to account for," Chiefs offensive coordinator Doug Pederson said. "We've got to try and get four hands on him when necessary. When you have an opportunity to go one on one with him you just have to anchor and use your hands properly against guys like that. You have to try the best you can to keep his hands down.

"However, on the other side of that, on the flip side of that, because he's tall, he'll play high, so in the run game sometimes, you can get your pad level a little bit lower than his and move him off the ball."

Campbell moves around the defensive line for the Cardinals, but you'll often find him at right end or sliding down shaded off the center in passing situations.

4. De'Anthony Thomas or Knile Davis breaking off a big return

The last time rookie De'Anthony Thomas played at the University of Phoenix Stadium, he was a standout playmaker for the Oregon Ducks as they took on the Kansas State Wildcats in the 2013 Fiesta Bowl.

In that game, Thomas took the opening kickoff 94 yards for a touchdown, helping the Ducks to a 35-17 victory.

Thomas obviously has fond memories of playing there.

"That's a great stadium," Thomas said of the University of Phoenix Stadium, where the Chiefs play on Sunday. "Great atmosphere. It's an exciting place to play."

Hoping for similar results on Sunday, Thomas is still only concerned with playing his role.

"Whenever I have the opportunity to get our team in great field position or score a touchdown, whatever I can do to help contribute, that's what I'm trying to do."

Chiefs special teams coach Dave Toub said both Thomas and Knile Davis will continue to rotate on kick returns.

"We have designed returns for each individual guy so if we want to call one return, it's going to be that returner," Toub explained. "Between those two, I don't have really a starter or a second-team guy. I think they're both equally as dangerous if at any time we could use any one of them."

5. Alex Smith attacking the Cardinals through the air

The Cardinals defense has been susceptible to the pass this season, ranking 27th in the NFL by allowing 263.3 yards per game through the air.

Over the past two games, tight end Anthony Fasano has caught two of the four touchdown passes for the Chiefs offense.

Smith talked about the continuity he's developed with Fasano.

"I really feel like – as far as us working together – I feel really good about us seeing the same things, talking a lot, reading his body language, anticipating throws and then trusting him," Smith said. "He's a guy you can really trust a lot of throws with. I think you've even seen the last two years the types of catches that he has made in traffic with people around him.

"It's certainly one of his strengths so as a quarterback you feel good throwing those balls into some of those tighter windows."

One statistic that's often thrown around regarding the Chiefs offense this season has been that no wide receiver has caught a touchdown pass yet, and it's something Reid doesn't seem to worry about.

"I don't worry about who gets them," Reid explained. "I'm concerned that you score them, whatever position it is. We've needed more than what we've done the past couple of weeks so we've got to do better there."

Besides Campbell and the talent up front, the Cardinals put a lot of responsibility on rookie safety Deone Bucannon (No. 36), who will often find himself playing in the box, much like the Chiefs have done with veteran Husain Abdullah this season. 

"It just goes to show the credibility and the accountability that they have and the trust that they have in Bucannon to play that spot," Chiefs offensive coordinator Doug Pederson explained. "It's a tough spot to be in. Are safeties asked to play in the box? Yeah, they are. But he's playing there every down. He's taking on offensive linemen and fullbacks.

"With that being said, he's done a really good job and [the Cardinals] like to cover up all five of your offensive linemen and it allows him and (Larry) Foote (No. 50) to kind of fast-flow, free-flow in there and make plays using their speed. Foote's a savvy veteran guy. He's been around the league a while and he can help [Bucannon] get lined up in there and so that's a plus to have a guy like Foote next to him."

On the outside, the Cardinals have plenty of talent at the cornerback position with Patrick Peterson and Antonio Cromartie.

"You give those guys a lot of respect," Pederson said. "You're on an island most of the time out there and again, with Arizona, kind of like Seattle, they present you man looks but they're playing zone so they kind of protect themselves a little bit.

"Your focus now is working the middle of the field, seams, things like that, short underneath routes, combination stuff."

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