You are going to see and hear all kinds of stats about how the Chicago Bears' defense has flipped a switch since they acquired Montez Sweat. While it is true that the defense has been much better since his acquisition, this was a unit that was trending up before him. Sweat extrapolated the growth., but this unit was already improving before he came.
The Chicago Bears defense was improving before the Montez Sweat trade
The Bears started things off rocky during their 0-4 start. However, that speaks to the idea that while they are 3-2 with Sweat, they are also 5-4 since that start. Things started to settle in the secondary, and T.J. Edwards started to play a lot better. Also, this is when Matt Eberflus started to call plays after Alan Williams left the staff.
In the first four weeks, the Bears allowed a 46.2% success rate, per RBSDM. That is down to 43.1% after week five. While their success rate allowed is 41.1% since the Sweat trade, it was also 41.2% overall from weeks five through eight.
That is mainly because their run defense has always been good. Their success rate from weeks five through eight is 20.9% on the ground. This is even better than what it was since the Sweat acquisition.
Passing success rate
Rushing success Rate
After Sweat trade
However, Sweat is making a big difference in the passing game. You can see that the EPA per passing play is down pretty significantly since the trade, and so is the success rate. This shows that the Bears are not just stopping the pass better on a down-to-down basis, they are also creating more sacks and turnovers since the Sweat acquisition.
Still, it is pretty clear in the numbers that this defense was starting to trend a lot better before the addition of Sweat. Sweat has made this an actual good unit, but the team was not nearly as bad as the first four weeks have indicated either.