There has been a lot of cross-pollination happening between the Dallas Cowboys and Oakland Raiders for some time, sometimes that happens among staffs that are friendly.
Jon Gruden returned to the Raiders a season ago and when he did he hired away Rich Bisaccia from the Cowboys. Following that they also signed Kyle Wilber, traded for Ryan Switzer, dealt Jamize Olawale and Jihad Ward to Dallas, and, of course, gave the Cowboys a star receiver in Amari Cooper in exchange for a first-round pick.