The Bills traded defensive tackle Marcell Dareus to the Jaguars on Oct. 27, and he first suited up for his new team the following week. Since then, the Bills rank last in the NFL in rushing yards allowed per game and the Jaguars rank first. The Bills are giving up 5.5 yards per carry in November, up from 3.8 YPC in the first two months of the season, while the Jaguars are down from 5.16 to 2.55 this month.
Is it that simple? Did Dareus suddenly fix the Jags' run defense and destroy the Bills?
Let's start with the Jaguars. In Dareus' three games with the team, they faced the Bengals (entered the game averaging 78.4 rushing yards), Chargers (88.9) and Browns (106.9) – not exactly great rushing offenses. (The league average through 11 weeks is 109 yards per game, with an average of 4.1 yards per carry.) While the team has improved with Dareus on the field, it also has done well with Dareus on the sideline.
Per ESPN's Bill Barnwell, the Jaguars are giving up 2.4 yards per carry on plays when Dareus is on the field and 2.7 YPC while he has been on the bench. So, he's helping, but it's not just him.
Worth noting, though, Jags defense since the acquisition:
With Marcell Dareus on the field: 30 carries, 71 yards (2.4 ypc)
Without Marcell Dareus on the field: 35 carries, 95 yards (2.7 ypc)
Dareus has helped, but Jags run D has stiffened with/without him https://t.co/6fsxk8GMR9
— Bill Barnwell (@billbarnwell) November 21, 2017
Dareus' absence on the Bills' defensive line seems like it has made a bigger difference. Their splits with and without Dareus are bad, but they need a little context:
Opponents running against the Bills
With Marcell Dareus on the field: 54 carries, 136 yards (2.5 yards per carry), 2 TD
Without Marcell Dareus: 214 carries, 1,061 yards (5.0 ypc), 14 TD
— Bill Barnwell (@billbarnwell) November 19, 2017
First, it's important to remember that the Bills had good games without the help of Dareus this season. The run defense played well against the Raiders two days after the trade, allowing only 54 rushing yards and 3.9 YPC in a 34-14 win, and it did OK in the Week 3 win against the Broncos while Dareus sat out with an injury, allowing 111 rushing yards and a 4.8 average.
It's also important to keep in mind that Dareus' role had diminished from what it was in previous years. He only played one-third of the Bills' defensive snaps before the trade.
The bigger question seems to be what has happened to the Bills' defense as a whole. The unit has been atrocious lately, giving up 135 points in the last three games. The defense has been healthy, outside of one game missed by cornerback E.J. Gaines, and starting linebacker Ramon Humber even returned to the lineup. Losing Dareus is a factor, but the issues feel bigger than one player.
The Bills have been gashed in their three latest games, giving up 194 rushing yards to the Jets, 298 to the Saints (the eighth-most in franchise history) and 146 to the Chargers. If you subtract those games from ESPN's stat (638 total yards on 124 runs, or 648 yards on 113 carries when you subtract the 11 QB kneels over that span that lost 10 yards, which seems to be the stat Barnwell is using), you get 413 yards allowed on 101 carries at any point this season without Dareus, or 4.1 YPC. That means the Bills were a league-average run defense without Dareus on the field, until the last three games.
What has happened since? The other defensive linemen have seen an increase in snaps since the trade, so maybe the new rotation puts too much on their plates. The pass rush hasn't gotten to the quarterback, defenders seem out of position, and they are missing tackles when they do get in position. Whatever is causing these issues, McDermott must fix it soon. Losing Dareus didn't help, but the Bills' problems go well beyond just that.