You lose a bunch of contributors and starters:

Pau'u (187 tackles, 1.5 TFL, 1.5 sacks, 1 INT, 3 PBU)
Takitaki (163 career tackles, 12.5 career sacks, 27.5 TFL)
Kaufusi (123 tackles, 14 TFL, 11.5 sacks, 3 PBU)
Z Anderson (111 tackles, 1 TFL, 3 INT, 2 PBU)
Pulsipher (84 tackles, 2.5 TFL, 1 PBU)
Hadley (76 tackles, 4 TFL, 3 PBU)
Shelton (58 tackles, 5 TFL, 2 INT, 7 PBU)
T Jacobson (43 tackles at BYU, 90 total, plus 1 INT)
Taliauli (43 tackles, 1 TFL)
Powell (DB) (14 tackles in 7 games)
Powell (LB) (11 tackles in 4 games this year)


That's at least 5 starters, maybe as many as 8 depending on how you count them and how the year ends.