Do you think it's possible that Seibold was signed for 5 years specifically to overhaul the roster?
I'm sure that was part of his mandate but one would think that if you're going to overhaul the Broncos roster you would start with culling the players who return the least value for money, i.e. McCullough and Boyd.
You would also think that keeping young guys with plenty of upside like Su'a would be high on the priority list. Especially when the club fought off several other clubs to sign him to a long term deal the year before.
He can "overhaul" the roster as much as he likes for the next few years but if Boyd and McCullough remain, then he's in for the same results.
We saw on the weekend that there's nowhere for Boyd to hide in the defensive line. 5/8, fullback, even if they stick him on a wing, he will be found out.