I think something else people should consider is that UK finished the season ranked 19th in the country (2nd in the SEC) in turnover margin last season. In 2013? UK was tied for 82nd in that category (9th in the SEC). For comparison, one other SEC team made a large leap in that category. Mizzou moved from 55th place in that ranking in 2013 to 20th place in 2014.
Also, in 2013, UK had only 3 interceptions on the season (that's horrendous). In the 2014 season, when our DB's became upperclassmen, that number grew from 3 interceptions to 15 (which was good for 23rd in the country in the rankings). 12 of which were recorded by defensive backs. In 2013, only 1 of the 3 interceptions were made by a defensive back. That's an enormous improvement.
The defense allowed only 215 passing yards per game, a solid 15 fewer yards per game than each of the previous two seasons (and good for 43rd in the country) and they continued to keep plays in front of them, allowing the second fewest long completions (of 40 yards or more) of any defense in the SEC. Our defense has a tremendous knack for keeping the ball in front of them and not allowing explosive plays. This upcoming year, I fully expect our boys to be able to time hits and deflection attempts, and allow even fewer passing yards per game.
For comparison of pass defenses, Muchamp's Gators (which had elite pass defenders on it), was ranked 41st. Others close to that were Mizzou (39th), Arkansas (37th).
Some may argue that teams didn't get as many pass yards because they would tend to run more against UK, which I would agree, but UK did markedly improve from 2013 to 2014 in team passing efficiency defense (accounts for completion percentage). In 2013, UK ranked 100th in this category, allowing a passing efficiency of 146.56 on average. In 2014, UK was now ranked in 57th in this category, allowing a passing efficiency of 126.55 on average.
For comparison of team pass efficiency defense, Alabama ranked 30th, allowing a passing efficiency of 116.53 (which is a very, very realistic leap for UK's pass defense). Ole Miss ranked 16th in that category, allowing a passing efficiency of 110.78. I believe UK could find somewhere in between these numbers next season.
I think it's very realistic that the defense improves all around. Runs will be easier to stop due to new-found depth in the front 7, a lot of quality players coming off of redshirt, experience, and a nice combo of size and speed. We'll likely have a bigger, stronger defensive line that will be stacked with 2-gap defensive tackles (If I had to guess today who would be the starting defensive tackles, I would say Melvin Lewis, Matt Elam, and Cory Johnson, which should cover a lot of real estate up front, an really take the pressure off the linebackers). Loving the way things are heading. If the cornerbacks are UK's biggest issue as of this spring, and they're improving off of those numbers, he's holding the defense to the same standard that he held them at while he was at Florida State, and things are going great.