The Bills defense has been super-stingy in the red zone through four games this season, and it's been a big reason why they've started 3-1.
Unsurprisingly, Buffalo's defense had its issues stopping opponents from scoring when they got inside the 20 last year.
Let's take a deep dive on the Bills' defensive red-zone efforts before Week Five's game against the Bengals.
Currently, Leslie Frazier's unit boasts a red-zone DVOA of -24.2 (negative is better for defense), the second-best in the NFL. Splitting that, Buffalo is third in red-zone pass defense DVOA and 13th in red-zone run defense DVOA.
Meanwhile, Cincinnati's offense has a red-zone DVOA of -40.9, which ranks 28th in the NFL.
Through four games, Bills' opponents have run 46 plays inside the red zone and have surrendered four touchdowns. Only the Seahawks and Raiders have allowed fewer touchdowns inside the red zone, per Pro Football Reference.
Going a step further, allowing four scores on 46 plays means 8.6 percent of the red-zone plays Buffalo's defense has faced have gone for a touchdown. That's the second-lowest percentage in football, and the current league average is 14.6 percent.
A season ago, they allowed a red-zone touchdown percentage (per play) of 15.4 percent (30 scores on 194 plays). In 2016, Sean McDermott's Panthers defense gave up 24 touchdowns on 214 red-zone plays, which equals 11.2 percent.
If the Bills defense continues to tighten inside the 20, Buffalo will be one of the league's most effective units this season.