I have a friend from Las Vegas who is a Broncos fan. I asked about Derby a few minutes ago and this is what he said (summarized):
Very athletic and makes an occasional spectacular play, but not instinctive and can't separate. High hopes entering the season but weaknesses surfaced. Fumbles quite a bit which is what got him in the doghouse with fans. Not bad on special teams. Some Denver fans were surprised when he was let go, but the team has so many problems right now they weren't going to care about the release of a backup tight end, other than ripping Elway for giving away another 5th round pick for nothing.
***
That's about it. Only the last part surprised me. I didn't realize they had traded for Derby, or that Denver has a similar tendency to ours in giving away later round picks.
During my friend's summary I couldn't help but thinking that Derby sounds like a tight end version of Devante Parker. And that's not bad, given the price we paid.