Buffalo Bills defensive coordinator Jim Schwartz will not return for the 2015 season, a league source said Monday night.

The reason, according to the source, was due to differing defensive philosophies.

Schwartz and new Bills coach Rex Ryan spoke about the direction of the defense within the last 24 hours.

Dennis Thurman, who was Ryan's defensive coordinator with the New York Jets the last two seasons, is expected to take over as defensive coordinator with the Bills.

Personnel sources said that Schwartz should receive strong interest from other teams looking to fill the role of defensive coordinator.

The Bills finished fourth overall in total defense, third in turnovers forced, and first in sacks.