Off top of my head, can't remember anybody other than DJ Taylor, who missed all of 2019 because of a torn ACL that happened when he wasn't even on a football field.
What kills you here is Robinson is the third LB they've lost if you're looking at the roster 2 months ago. There was the freshman who left in the summer (Jaquez Keyes) and the second-year guy who was medically DQ'd (Tommy Bebie).
They still feel good about the top 5, though. That's Chase Jones, Dylan Hazen, Quincy Bryant, Jacob Roberts and Aiden Hall. I think that's still enough to handle losing Robinson ... but they have zero room for error (or injury).