I received a notification through about this story, I looked to the NFL website and realised they had taken it from Manish. So believe what you like but I would take anything with a pinch of salt.
According to the report, referencing a friend of Rex, Ryan is pissed about losing DRC to the Giants.
Another interesting note came from within the facility (apparently):
I can understand that Rex needs to win now and if Idzik is in a long term strategy that may cause some problems. However Woody and John are not idiots and they know football. If they haven't given Rex the weapons to win a Superbowl, they can't blame him for not doing it.
I didn't like the guarantees in DRC's contract, he has been one of the best corners, but he's also been one of the worst corners. His inconsistency is a nightmare and he gives up a lot of plays deep, something that would annoy just about everyone in the building. I did like James Jones contract and think Oakland have done well there.
I don't know if Rex is actually pissed, or it was an expression of disappointment from a man who loves winning. We'll never really know. I'm sure there will be multiple stories trying to drive a wedge between coach and management, but until we see any legitimate concerns, I'm taking this all with a pinch of salt.