The last defensive position group to look at is the defensive backs.
After having a really good year in 2016, the Bruins took a step back in 2017. In 2016, UCLA was ranked 7th nationally in Defensive Pass Efficiency, but the team dropped to 72nd last season. After allowing just 12 passing touchdowns in 2016, the Bruin defense allowed 19 passing touchdowns in 2017.
In both cases, a lot of the blame for these stats has to fall on the secondary. In order for the Bruin defense to get better, the secondary must improve and that starts by allowing fewer touchdown passes.