The 2018 NFL coaching carousel is moving incredibly quickly, and on Monday morning Martin Lewis joined the rapidly-expanding list of coaches to exit their teams, as he stepped down as coach of the Cincinnati Bengals. According to CBS Sports NFL Insider Jason La Canfora, Marvin Lewis will not be returning as the team's head coach in 2019.

Lewis spent 16 years with the Bengals after being hired in 2003, and compiled a record of 131-122-3 during that time. He also was named Coach of the Year in 2009, when the Bengals won the AFC North with a 10-6 record.

Prior to Lewis' arrival, the Bengals had not made the playoffs since 1990. He returned the team to respectability with back-to-back 8-8 seasons before they finally made the playoffs in 2005. It took several years after that before they returned to the postseason, but even after making five-straight appearances they could never break through with a playoff win.

During his 16 years in Cincinnati, the Bengals made the playoffs seven times and lost all seven playoff games they played. Lewis' seven postseason losses are the most of any coach who has never won a postseason game. Additionally, this year was the third-consecutive season they missed out on the playoffs following those five-straight berths from 2011 through 2015.

The longtime Bengals coach was almost fired by the team last offseason, and it even got to the point that Lewis reportedly told his staff that he would be leaving the team to pursue other opportunities. Instead, Lewis was given a two-year contract extension and remained with the Bengals this season. The team dealt with injuries all year and eventually finished with a 6-10 record.

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Lewis fired a coordinator midseason for the second-consecutive year, parting ways with offensive coordinator Ken Zampese two games into the 2017 season and letting go of defensive coordinator Teryl Austin in November of this season. Lewis brought in former Browns coach Hue Jackson as a special assistant to help with the defense, but it did not improve.

Lewis turned 60 years old earlier this season, but his coaching career is likely not over. It's unknown whether he'll be a candidate for head coaching jobs elsewhere, but he is still a respected coach and strong defensive mind, so he will presumably land elsewhere if he wants to continue in the league.