Edited the link. Try it now.
https://www.footballstudyhall.com/2015/9/4/9254347/a-better-way-to-measure-returning-experience
I think there are a few factors at play.
1. Returning starters (experience / youth) whatever you want to call it.
2. Is the scheme consistent. IS the defense being taught the same to the players with same concepts year after year.
3. Talent
4. Are players getting on the field by choice or by necessity
My assessment:
1. Our starting secondary was Shenault, Huff, Winfield, and Smith.
Shenault changed positions, and now we have two rookies getting significant time.
2. The scheme was not consistent for the veterans who are playing. Winfield, Huff, and Shenault all are playing under a new scheme as of 2017. (So after learning for a year or two, it's changed and vastly different just in whether the CB's are taught to look back or not when defending passes).
3. Talent. Outside of Winfield, we don't have an upperclassman who would look like a Buddy-Calhoun, a Eric Murray, or a Jalen Myrick. Also hurting is with Winfield off the team, we probably lost our leader in the secondary who would have been that strong point to help the secondary play well. Now Huff or Shenault are essentially the leader of the defense for the freshman to rely on. In my book that's a significant gap.
4. Terell Smith is playing and isn't doing it by necessity, but Jordan Howden is playing by necessity. I don't think it was ever the plan for a freshman walk-on to be playing as much as he is at safety.
So in all four areas, we're subpar.
From the study, if this was our linebacker core or even our Defensive line, it would be easier to cover it up. But instead, we don't have NFL caliber talent, we changed the way the secondary has to play, we are thin on numbers so players are playing by necessity, and now we are playing two freshmen, one who was not heavily recruited.
Part of the issue is we had two safeties leave from PJ's first class, but that also happened after PJ had mostly wrapped up recruiting on his 2018 class which was heavy on O-Line due to deficits there. Other part of the issue is we lost significant players due to transfer / expulsion.