On January 13,2010, Crennel hired as the Kansas City Chiefs defensive coordinator, reuniting him with offensive coordinator Charlie Weis and General Manager Scott Pioli from their days with the Patriots.
On January 13,2010, Crennel officially signed with the Kansas City Chiefs. He replaced Clancy Pendergast as the team's defensive coordinator, reuniting him with offensive coordinator Charlie Weis and General Manager Scott Pioli from their days with the Patriots.