Although Marvin Lewis has signed an extension to remain as Bengals head coach, he’ll return in 2018 without his defensive coordinator. Paul Guenther will leave Cincinnati after 13 seasons to explore other opportunities, according to Jason La Canfora of CBSSports.com (Twitter link). Guenther, whose contract has expired, has enjoyed a long working relationship with Lewis, as the two overlapped for one year with the Redskins before Guenther was hired by the Bengals in 2005. After serving as a defensive staffer for nine seasons, Guenther took over as Cincinnati’s defensive coordinator after Mike Zimmer left to become the Vikings’ head coach. The Bengals have finished 14th, 10, 17th, and 14th in defensive DVOA in four full seasons under Guenther.