There is no doubt about it that Roquan Smith made a big difference to the Baltimore Ravens' defense. While it is fair to note that the Ravens' defense got healthy towards the end of the season, and the schedule softened up late, it is also fair to note that once Smith was added to the lineup, the Ravens defense immediately took off.
The value of Roquan Smith to the Baltimore Ravens defense
How significant was his addition?
According to RBSDM, the Ravens expected points allowed per play*100 is 7.6 before Smith was on the team. That number dropped to -7.8. The difference is as big as it looks, they went from 28 in the first eight games in EPA/Play to fifth in the final eight games. Their overall success rate dropped from 47% to 41.9% in that span.
In terms of passing defense, the Ravens' expected points allowed was at 10.9 without Smith. It dropped to -0.6 with Smith. The success rate of the Ravens defense dropped from 48.4% to 44.6%
The rush defense saw a similar improvement. They went from 0.1 in rushing EPA allowed to -18.8, which is a significant difference. They were 24th after eight weeks, but third in the final eight weeks. Overall, they finished eighth despite such a slow start. They also went from a 43.8% rushing success rate allowed to a 37.9% rate. That was a jump from 23rd to 10th.
It does not hurt that Josh Allen, Joe Burrow, and Tua Tagovailoa were in the first eight games, when Mitch Trubisky, Desmond Ridder, and Kenny Pickett were the big names in the back half. The Ravens happened to miss Joe Burrow the second time around, and Deshaun Watson was a shell of himself.
The Ravens also saw guys like Tyus Bowser get healthy at the right time, and Mike MacDonald found his footing as coordinator. Still, these factors definitely matter, but that type of drastic improvement also resulted from a big change.
The Baltimore Ravens added Roquan Smith and it completely changed the defense. It made Patrick Queen better, and in the middle of the defense, both the running and passing defense improved. The Baltimore Ravens immediately extended Roquan Smith and when you think that this change happened that drastically it is easy to understand why.