There's been rumblings about locker room chemistry, and the move may be more about Amari Cooper than Crabs. Nelson will be a legit mentor and tutor for Cooper, and Gruden obviously sees a big role for Nelson in whatever offense he has planned. There's been speculation, but nobody has a solid take on what a modern Jon Gruden offense will look like. Crabtree's also been nicked up plenty the last two seasons, though the man is a warrior. Late in 2017 there were rumors he took himself out of games late, though they could never be attributed between him or the coaches.
There has been a rumor out there for awhile that the Raiders Oline intentionally, in a premeditated fashion, allowed David Carr to get sacked until he was hurt.
The desire to do so allegedly stemmed from Carr preaching to them (literally from the bible) in reference to the National Anthem protest for which he believed all should stand as a team. Some other players beyond the OL were supposedly aware of the "plan" and the incident contributed to Oak being among the most divided locker room.................. goes the story.
Not sure if it ever happened that way, or if it did, Crab was one of the "aware" but he was one of a couple of players sitting on a cooler with Marshawn Lynch during the National Anthem on Sunday Night football early in the season, so Crab was definitely on the other side of Carr in the divide.