Yep, Tennessee wouldn't trade him for a bunch of reasons- 1) as you said, he's a good player when healthy, 2) picking up his option would have made him one of the highest paid RTs in the league but they'll have a bunch of different avenues to pursue if they want to keep him past '19, and 3) there isn't much of a trade market for RTs- RT is neck & neck with FS/SS for the lowest valued position in the league.
Better tell that to Elway...