Every NFL fan circled this date on their calendars when the 2021 schedule was released: a rematch of last season's AFC Championship Game. Buffalo and Kansas City have proven for the second straight season that they are two of the league's best squads.

On Sunday night at 8:20 p.m. on NBC's Sunday Night Football, the AFC rivals will meet again at Arrowhead Stadium. Washington played Buffalo in Week 2 of this season, losing by a gnarly final of 43-21 in an all-out showcase by the Bills. The Burgundy and Gold will still be heavily invested in Sunday's Bills-Chiefs game as they face the defending AFC Champions one week later at FedEx Field on Oct. 17.

Here are three things for Washington fans to look for in Bills-Chiefs...

Can Buffalo contain Mahomes?

Patrick Mahomes is the NFL's best and most dynamic quarterback, hence the reason he was given a handsome $503 million contract this past summer. When Washington faces the Chiefs one week from Sunday, they will watch game film on Buffalo's defense, and perhaps use it as a template for how to hinder the league's highest-powered offense.

Buffalo has the best defense in the league when it comes to limiting opposing quarterbacks. Just ask Taylor Heinicke, who was held to a 58.3 completion percentage, two passing touchdowns and two interceptions in Washington's Week 2 loss. 

The Bills have only allowed three total passing touchdowns this season, good enough for second in the NFL. They lead the league with just 148.8 passing yards allowed per game. Now, if anyone can crack that code and defeat the vaunted Buffalo defense, it's Mahomes.

A struggling Washington defense will have their hands full with the likes of Mahomes, Tyreek Hill, and Travis Kelce next Sunday. If the Bills can contain that trio, the D.C. defensive unit could attempt to replicate their strategy. 

How do Bills running backs perform?

Buffalo has handled running back duty on a committee basis this season. Devin Singeltary and Zach Moss have split carries thus far in 2021, with Moss usually snagging a slight advantage in terms of workload.

While Kansas City has figured to be one of the league's best overall teams this year, it certainly isn't because of its run defense. The Chiefs have the conceded the league's most rushing touchdowns, fourth-most rushing yards, and highest average yards per carry. Simply put, their run defense is in shambles.

However, Buffalo is the definition of a pass-heavy team. Josh Allen likes to have the ball in his hands when the Bills' offense is on the field, and with targets like Stefon Diggs, Emmanuel Sanders, Cole Beasley and Dawson Knox, it's hard to blame him.

If Buffalo were to plow through the Chiefs' defensive unit, it's likely they'd have to forego their pass-heavy offense in favor of a more run-friendly game plan on Sunday. If Moss and Singletary carve up Kansas City's defense, Antonio Gibson and J.D. McKissic should be able to do much of the same one week later. Keep an eye on how Buffalo's two-headed monster at RB is utilized at Arrowhead. 

Josh Allen outside the pocket

Remember how bad Kansas City's run defense is? The story isn't much better when it comes to the passing game. Conceding the third-highest yards per attempt rate in the league, the Chiefs will pray that Josh Allen will not play like his usual self on Sunday.

Chances are, though, that he will. While Allen is known to be a bullseye-accurate thrower, he can hold his own outside the pocket as well. He could give the Chiefs fits if their defensive line isn't able to close the pocket quickly.

Heinicke has displayed a knack for extending plays this season, too, in which he has put up historically-great numbers as a starter. He's a capable and mobile runner once the play breaks down, so he in particular will look to see how Allen navigates Sunday night's matchup. If Allen is spry rolling out, extending plays, or rushing past the line of scrimmage, Heinicke will likely try to do the same a week later vs. Kansas City to help Washington's offense in a game it will need to score lots of points.