Griz do only return three defensive starters, so I would say, to start the season, there is no way this defense will be as productive, and I'm worried about the switch to a 3-4 if that's a for sure thing. Montana has always made a living on pass rushers and disruption at the line of scrimmage, and I hate to see that mentality go away.
However, there are bright sports in my opinion.
DL - Kidder will be a monster again, and is the heart and soul of the entire team. Ryan Johnson is a beast, and is full ready to play every single down. Peevey will get healthy and will also add another 10 pounds, and I think he is a force next year. Hopefully, the DT transfer is as advertised as well.
LB - I agree with PR in that it's premature to already anoint the new LBs group, and there is no way any of them are as fast as KVA was on the edge. But, there's no denying, the group is deep and loaded with size and toughness. Strahm and Buss are can't miss dudes, and Jimmy Banks sure looks the part. Alex Thomas is also ready to play a big role, and I wouldn't be surprised if you start to see what Dante Olson, David F. and Sirmon can do in limited situations, much like we saw from Strahm and Buss this year. So, while there is no way you just replace KVA, Kose and Gamboa, the talent and upside is there.
Back end: JR Nelson is the best returning cover corner in the Big Sky imho. He's a lockdown guy now. The competition to start on the other side will be fierce between Ryan McKinley and Markell Sanders but I thought both looked great this season. Yamen Sanders I feel brings a great toughness to the safety position. He's not afraid of anything. If he improves his pass coverage, he's an All-American. Manu wil be better next year too, and it's possible Dellasara will be back too. And while I know everyone wants Evan Epperly to be the next great Griz safety from Montana, the name you will get to know over the next couple of years is Jerrin Williams. He's an absolute athletic freak.
So, while I don't think the 2016 Griz defense could open the season like the 2015 defense did, I think Montana is loaded with young talent, and hopefully, a few more additions to the DL through transfers, and/or the emergence of Jesse Sims and Donald Bedell at DE, and, eventually, the defense should be the Griz defense we've all grown accustomed to loving.