The New Orleans Saints have not hid the fact that they still want to improve the defensive side of the ball in 2018. The Saints traded a 2019 first round pick to trade up in the first round of the 2018 NFL Draft and select Marcus Davenport to rush the passer opposite Cam Jordan. The first free agents the Saints brought in this offseason were all on defense: Patrick Robison, Kurt Coleman, Demario Davis, and re-signing Alex Okafor.
If you break up the defense into four categories - defensive line, linebackers, cornerbacks and safeties, it would be the defensive line and linebackers that would be the two weakest of the four groups.