After Don Brown left, UConn's D has been deteriorating. In 2016, Diaco's last year, UConn's Total Defense ranked #65, which was the worst performance by a UConn defense in a decade. And, Diaco's defense in 2016 was made to look better by his ball control offense. (By the way, there is a high correlation between a team's offensive time of possession and it's total defense ranking. It's pretty logical as the more time an offense has the ball, the more plays they can run.) In 2017, UConn changed the defensive scheme with a roster that was not made to run the defense, and ran a fast paced offense which was ranked 75th in time of possession, and the defense imploded. In 2018, the defensive stats should look better as the team will be more comfortable running the 3-3-5 and the offense probably won't be as fast paced. I'm not saying the defense WILL be better, but the defensive stats should be better.
As for talent, Diaco did not recruit any decent edge rushers and it was obvious last year. Plus, Diaco's defense gave wide cushions to receivers which masked our DBs' lack of speed. It will take time to upgrade the talent, but I like what i have seen so far.
In my opinion, year 2 will be another tough year for the defense, but 2019 should be a much better year.