The Ravens will see a second assistant coach go to Buffalo to join new Head Coach Sean McDermott's staff.
Secondary Coach Leslie Frazier will become the Bills defensive coordinator. The Bills confirmed the deal in principle Friday afternoon, along with the arrival of Offensive Line Coach and Run Game Coordinator Juan Castillo.
Frazier, Castillo and McDermott all worked together as assistants with the Philadelphia Eagles, along with Ravens Head Coach John Harbaugh. The Ravens reportedly gave Frazier permission to interview for the promotion.
Frazier, 57, spent just one season with the Ravens, and he helped the secondary make steady improvement under his guidance. When Frazier arrived in Baltimore a year ago, he preached the importance of a ball-hawking mentality.
The Ravens defense took to his teaching and responded by collecting a league-high 18 interceptions, compared to a franchise-low six interceptions the previous season. The unit ranked No. 9 in passing defense under Frazier's direction.
With Frazier leaving, the Ravens could look to bring in another defensive assistant, or fill the vacancy internally. A potential in-house candidate could be Chris Hewitt, who has been the team's defensive backs coach for the last two seasons.